diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index 773c1dfd..81f87c56 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -1,4 +1,4 @@
-# Copyright 2023 Google LLC
+# Copyright 2024 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:2f155882785883336b4468d5218db737bb1d10c9cea7cb62219ad16fe248c03c
-# created: 2023-11-29T14:54:29.548172703Z
+  digest: sha256:5a4c19d17e597b92d786e569be101e636c9c2817731f80a5adec56b2aa8fe070
+# created: 2024-04-12T11:35:58.922854369Z
diff --git a/.github/sync-repo-settings.yaml b/.github/sync-repo-settings.yaml
index f1068589..d85818a5 100644
--- a/.github/sync-repo-settings.yaml
+++ b/.github/sync-repo-settings.yaml
@@ -7,24 +7,24 @@ branchProtectionRules:
   requiredStatusCheckContexts:
     - 'style-check'
     - 'docs'
-    - 'unit (3.6)'
-    - 'unit (3.6, cpp)'
-    - 'unit (3.7)'
     - 'unit (3.7, cpp)'
+    - 'unit (3.7, python)'
     - 'unit (3.7, upb)'
-    - 'unit (3.8)'
     - 'unit (3.8, cpp)'
+    - 'unit (3.8, python)'
     - 'unit (3.8, upb)'
-    - 'unit (3.9)'
     - 'unit (3.9, cpp)'
+    - 'unit (3.9, python)'
     - 'unit (3.9, upb)'
-    - 'unit (3.10)'
     - 'unit (3.10, cpp)'
+    - 'unit (3.10, python)'
     - 'unit (3.10, upb)'
-    - 'unit (3.11)'
+    - 'unit (3.11, python)'
     - 'unit (3.11, upb)'
-    - 'unit (3.12)'
+    - 'unit (3.12, python)'
     - 'unit (3.12, upb)'
+    - 'prerelease (3.12, python)'
+    - 'prerelease (3.12, upb)'
     - cover
     - OwlBot Post Processor
     - 'cla/google'
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e28374fe..edbc2141 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -19,7 +19,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python 3.8
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: 3.8
       - name: Install black
@@ -31,7 +31,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python 3.9
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: "3.9"
       - name: Install nox.
@@ -39,22 +39,30 @@ jobs:
       - name: Build the documentation.
         run: nox -s docs
   unit:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
-        python: ['3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
-        variant: ['', 'cpp', 'upb']
+        python: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
+        variant: ['cpp', 'python', 'upb']
+        # TODO(https://github.com/googleapis/proto-plus-python/issues/389):
+        # Remove the 'cpp' implementation once support for Protobuf 3.x is dropped.
+        # The 'cpp' implementation requires Protobuf == 3.x however version 3.x
+        # does not support Python 3.11 and newer. The 'cpp' implementation
+        # must be excluded from the test matrix for these runtimes.
         exclude:
           - variant: "cpp"
             python: 3.11
           - variant: "cpp"
             python: 3.12
+          - variant: "cpp"
+            python: 3.13
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python }}
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python }}
+          allow-prereleases: true
       - name: Install nox
         run: |
           pip install nox
@@ -68,12 +76,38 @@ jobs:
         env:
           COVERAGE_FILE: .coverage-${{ matrix.variant }}-${{ env.PYTHON_VERSION_TRIMMED }}
         run: |
-          nox -s unit${{ matrix.variant }}-${{ env.PYTHON_VERSION_TRIMMED }}
+          nox -s "unit-${{ env.PYTHON_VERSION_TRIMMED }}(implementation='${{ matrix.variant }}')"
       - name: Upload coverage results
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
-          name: coverage-artifacts
+          name: coverage-artifact-${{ matrix.variant }}-${{ env.PYTHON_VERSION_TRIMMED }}
           path: .coverage-${{ matrix.variant }}-${{ env.PYTHON_VERSION_TRIMMED }}
+  prerelease:
+    runs-on: ubuntu-22.04
+    strategy:
+      matrix:
+        python: ['3.12']
+        variant: ['python', 'upb']
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python ${{ matrix.python }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python }}
+          allow-prereleases: true
+      - name: Install nox
+        run: |
+          pip install nox
+      - name: Run unit tests
+        env:
+          COVERAGE_FILE: .coverage-prerelease-${{ matrix.variant }}
+        run: |
+          nox -s "prerelease_deps(implementation='${{ matrix.variant }}')"
+      - name: Upload coverage results
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-artifact-prerelease-${{ matrix.variant }}
+          path: .coverage-prerelease-${{ matrix.variant }}
   cover:
     runs-on: ubuntu-latest
     needs:
@@ -82,7 +116,7 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v4
     - name: Setup Python
-      uses: actions/setup-python@v4
+      uses: actions/setup-python@v5
       with:
         python-version: "3.10"
     - name: Install coverage
@@ -90,11 +124,11 @@ jobs:
         python -m pip install --upgrade setuptools pip wheel
         python -m pip install coverage
     - name: Download coverage results
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
-        name: coverage-artifacts
         path: .coverage-results/
     - name: Report coverage results
       run: |
-        coverage combine .coverage-results/.coverage*
+        find .coverage-results -type f -name '*.zip' -exec unzip {} \;
+        coverage combine .coverage-results/**/.coverage*
         coverage report --show-missing --fail-under=100
diff --git a/.kokoro/docker/docs/Dockerfile b/.kokoro/docker/docs/Dockerfile
index 8e39a2cc..bdaf39fe 100644
--- a/.kokoro/docker/docs/Dockerfile
+++ b/.kokoro/docker/docs/Dockerfile
@@ -80,4 +80,8 @@ RUN wget -O /tmp/get-pip.py 'https://bootstrap.pypa.io/get-pip.py' \
 # Test pip
 RUN python3 -m pip
 
+# Install build requirements
+COPY requirements.txt /requirements.txt
+RUN python3 -m pip install --require-hashes -r requirements.txt
+
 CMD ["python3.8"]
diff --git a/.kokoro/docker/docs/requirements.in b/.kokoro/docker/docs/requirements.in
new file mode 100644
index 00000000..816817c6
--- /dev/null
+++ b/.kokoro/docker/docs/requirements.in
@@ -0,0 +1 @@
+nox
diff --git a/.kokoro/docker/docs/requirements.txt b/.kokoro/docker/docs/requirements.txt
new file mode 100644
index 00000000..0e5d70f2
--- /dev/null
+++ b/.kokoro/docker/docs/requirements.txt
@@ -0,0 +1,38 @@
+#
+# This file is autogenerated by pip-compile with Python 3.9
+# by the following command:
+#
+#    pip-compile --allow-unsafe --generate-hashes requirements.in
+#
+argcomplete==3.2.3 \
+    --hash=sha256:bf7900329262e481be5a15f56f19736b376df6f82ed27576fa893652c5de6c23 \
+    --hash=sha256:c12355e0494c76a2a7b73e3a59b09024ca0ba1e279fb9ed6c1b82d5b74b6a70c
+    # via nox
+colorlog==6.8.2 \
+    --hash=sha256:3e3e079a41feb5a1b64f978b5ea4f46040a94f11f0e8bbb8261e3dbbeca64d44 \
+    --hash=sha256:4dcbb62368e2800cb3c5abd348da7e53f6c362dda502ec27c560b2e58a66bd33
+    # via nox
+distlib==0.3.8 \
+    --hash=sha256:034db59a0b96f8ca18035f36290806a9a6e6bd9d1ff91e45a7f172eb17e51784 \
+    --hash=sha256:1530ea13e350031b6312d8580ddb6b27a104275a31106523b8f123787f494f64
+    # via virtualenv
+filelock==3.13.1 \
+    --hash=sha256:521f5f56c50f8426f5e03ad3b281b490a87ef15bc6c526f168290f0c7148d44e \
+    --hash=sha256:57dbda9b35157b05fb3e58ee91448612eb674172fab98ee235ccb0b5bee19a1c
+    # via virtualenv
+nox==2024.3.2 \
+    --hash=sha256:e53514173ac0b98dd47585096a55572fe504fecede58ced708979184d05440be \
+    --hash=sha256:f521ae08a15adbf5e11f16cb34e8d0e6ea521e0b92868f684e91677deb974553
+    # via -r requirements.in
+packaging==24.0 \
+    --hash=sha256:2ddfb553fdf02fb784c234c7ba6ccc288296ceabec964ad2eae3777778130bc5 \
+    --hash=sha256:eb82c5e3e56209074766e6885bb04b8c38a0c015d0a30036ebe7ece34c9989e9
+    # via nox
+platformdirs==4.2.0 \
+    --hash=sha256:0614df2a2f37e1a662acbd8e2b25b92ccf8632929bc6d43467e17fe89c75e068 \
+    --hash=sha256:ef0cc731df711022c174543cb70a9b5bd22e5a9337c8624ef2c2ceb8ddad8768
+    # via virtualenv
+virtualenv==20.25.1 \
+    --hash=sha256:961c026ac520bac5f69acb8ea063e8a4f071bcc9457b9c1f28f6b085c511583a \
+    --hash=sha256:e08e13ecdca7a0bd53798f356d5831434afa5b07b93f0abdf0797b7a06ffe197
+    # via nox
diff --git a/.kokoro/requirements.in b/.kokoro/requirements.in
index ec867d9f..fff4d9ce 100644
--- a/.kokoro/requirements.in
+++ b/.kokoro/requirements.in
@@ -1,5 +1,5 @@
 gcp-docuploader
-gcp-releasetool>=1.10.5 # required for compatibility with cryptography>=39.x
+gcp-releasetool>=2 # required for compatibility with cryptography>=42.x
 importlib-metadata
 typing-extensions
 twine
@@ -8,3 +8,4 @@ setuptools
 nox>=2022.11.21 # required to remove dependency on py
 charset-normalizer<3
 click<8.1.0
+cryptography>=42.0.5
diff --git a/.kokoro/requirements.txt b/.kokoro/requirements.txt
index e5c1ffca..51f92b8e 100644
--- a/.kokoro/requirements.txt
+++ b/.kokoro/requirements.txt
@@ -93,31 +93,41 @@ colorlog==6.7.0 \
     # via
     #   gcp-docuploader
     #   nox
-cryptography==41.0.6 \
-    --hash=sha256:068bc551698c234742c40049e46840843f3d98ad7ce265fd2bd4ec0d11306596 \
-    --hash=sha256:0f27acb55a4e77b9be8d550d762b0513ef3fc658cd3eb15110ebbcbd626db12c \
-    --hash=sha256:2132d5865eea673fe6712c2ed5fb4fa49dba10768bb4cc798345748380ee3660 \
-    --hash=sha256:3288acccef021e3c3c10d58933f44e8602cf04dba96d9796d70d537bb2f4bbc4 \
-    --hash=sha256:35f3f288e83c3f6f10752467c48919a7a94b7d88cc00b0668372a0d2ad4f8ead \
-    --hash=sha256:398ae1fc711b5eb78e977daa3cbf47cec20f2c08c5da129b7a296055fbb22aed \
-    --hash=sha256:422e3e31d63743855e43e5a6fcc8b4acab860f560f9321b0ee6269cc7ed70cc3 \
-    --hash=sha256:48783b7e2bef51224020efb61b42704207dde583d7e371ef8fc2a5fb6c0aabc7 \
-    --hash=sha256:4d03186af98b1c01a4eda396b137f29e4e3fb0173e30f885e27acec8823c1b09 \
-    --hash=sha256:5daeb18e7886a358064a68dbcaf441c036cbdb7da52ae744e7b9207b04d3908c \
-    --hash=sha256:60e746b11b937911dc70d164060d28d273e31853bb359e2b2033c9e93e6f3c43 \
-    --hash=sha256:742ae5e9a2310e9dade7932f9576606836ed174da3c7d26bc3d3ab4bd49b9f65 \
-    --hash=sha256:7e00fb556bda398b99b0da289ce7053639d33b572847181d6483ad89835115f6 \
-    --hash=sha256:85abd057699b98fce40b41737afb234fef05c67e116f6f3650782c10862c43da \
-    --hash=sha256:8efb2af8d4ba9dbc9c9dd8f04d19a7abb5b49eab1f3694e7b5a16a5fc2856f5c \
-    --hash=sha256:ae236bb8760c1e55b7a39b6d4d32d2279bc6c7c8500b7d5a13b6fb9fc97be35b \
-    --hash=sha256:afda76d84b053923c27ede5edc1ed7d53e3c9f475ebaf63c68e69f1403c405a8 \
-    --hash=sha256:b27a7fd4229abef715e064269d98a7e2909ebf92eb6912a9603c7e14c181928c \
-    --hash=sha256:b648fe2a45e426aaee684ddca2632f62ec4613ef362f4d681a9a6283d10e079d \
-    --hash=sha256:c5a550dc7a3b50b116323e3d376241829fd326ac47bc195e04eb33a8170902a9 \
-    --hash=sha256:da46e2b5df770070412c46f87bac0849b8d685c5f2679771de277a422c7d0b86 \
-    --hash=sha256:f39812f70fc5c71a15aa3c97b2bbe213c3f2a460b79bd21c40d033bb34a9bf36 \
-    --hash=sha256:ff369dd19e8fe0528b02e8df9f2aeb2479f89b1270d90f96a63500afe9af5cae
+cryptography==42.0.5 \
+    --hash=sha256:0270572b8bd2c833c3981724b8ee9747b3ec96f699a9665470018594301439ee \
+    --hash=sha256:111a0d8553afcf8eb02a4fea6ca4f59d48ddb34497aa8706a6cf536f1a5ec576 \
+    --hash=sha256:16a48c23a62a2f4a285699dba2e4ff2d1cff3115b9df052cdd976a18856d8e3d \
+    --hash=sha256:1b95b98b0d2af784078fa69f637135e3c317091b615cd0905f8b8a087e86fa30 \
+    --hash=sha256:1f71c10d1e88467126f0efd484bd44bca5e14c664ec2ede64c32f20875c0d413 \
+    --hash=sha256:2424ff4c4ac7f6b8177b53c17ed5d8fa74ae5955656867f5a8affaca36a27abb \
+    --hash=sha256:2bce03af1ce5a5567ab89bd90d11e7bbdff56b8af3acbbec1faded8f44cb06da \
+    --hash=sha256:329906dcc7b20ff3cad13c069a78124ed8247adcac44b10bea1130e36caae0b4 \
+    --hash=sha256:37dd623507659e08be98eec89323469e8c7b4c1407c85112634ae3dbdb926fdd \
+    --hash=sha256:3eaafe47ec0d0ffcc9349e1708be2aaea4c6dd4978d76bf6eb0cb2c13636c6fc \
+    --hash=sha256:5e6275c09d2badf57aea3afa80d975444f4be8d3bc58f7f80d2a484c6f9485c8 \
+    --hash=sha256:6fe07eec95dfd477eb9530aef5bead34fec819b3aaf6c5bd6d20565da607bfe1 \
+    --hash=sha256:7367d7b2eca6513681127ebad53b2582911d1736dc2ffc19f2c3ae49997496bc \
+    --hash=sha256:7cde5f38e614f55e28d831754e8a3bacf9ace5d1566235e39d91b35502d6936e \
+    --hash=sha256:9481ffe3cf013b71b2428b905c4f7a9a4f76ec03065b05ff499bb5682a8d9ad8 \
+    --hash=sha256:98d8dc6d012b82287f2c3d26ce1d2dd130ec200c8679b6213b3c73c08b2b7940 \
+    --hash=sha256:a011a644f6d7d03736214d38832e030d8268bcff4a41f728e6030325fea3e400 \
+    --hash=sha256:a2913c5375154b6ef2e91c10b5720ea6e21007412f6437504ffea2109b5a33d7 \
+    --hash=sha256:a30596bae9403a342c978fb47d9b0ee277699fa53bbafad14706af51fe543d16 \
+    --hash=sha256:b03c2ae5d2f0fc05f9a2c0c997e1bc18c8229f392234e8a0194f202169ccd278 \
+    --hash=sha256:b6cd2203306b63e41acdf39aa93b86fb566049aeb6dc489b70e34bcd07adca74 \
+    --hash=sha256:b7ffe927ee6531c78f81aa17e684e2ff617daeba7f189f911065b2ea2d526dec \
+    --hash=sha256:b8cac287fafc4ad485b8a9b67d0ee80c66bf3574f655d3b97ef2e1082360faf1 \
+    --hash=sha256:ba334e6e4b1d92442b75ddacc615c5476d4ad55cc29b15d590cc6b86efa487e2 \
+    --hash=sha256:ba3e4a42397c25b7ff88cdec6e2a16c2be18720f317506ee25210f6d31925f9c \
+    --hash=sha256:c41fb5e6a5fe9ebcd58ca3abfeb51dffb5d83d6775405305bfa8715b76521922 \
+    --hash=sha256:cd2030f6650c089aeb304cf093f3244d34745ce0cfcc39f20c6fbfe030102e2a \
+    --hash=sha256:cd65d75953847815962c84a4654a84850b2bb4aed3f26fadcc1c13892e1e29f6 \
+    --hash=sha256:e4985a790f921508f36f81831817cbc03b102d643b5fcb81cd33df3fa291a1a1 \
+    --hash=sha256:e807b3188f9eb0eaa7bbb579b462c5ace579f1cedb28107ce8b48a9f7ad3679e \
+    --hash=sha256:f12764b8fffc7a123f641d7d049d382b73f96a34117e0b637b80643169cec8ac \
+    --hash=sha256:f8837fe1d6ac4a8052a9a8ddab256bc006242696f03368a4009be7ee3075cdb7
     # via
+    #   -r requirements.in
     #   gcp-releasetool
     #   secretstorage
 distlib==0.3.7 \
@@ -136,9 +146,9 @@ gcp-docuploader==0.6.5 \
     --hash=sha256:30221d4ac3e5a2b9c69aa52fdbef68cc3f27d0e6d0d90e220fc024584b8d2318 \
     --hash=sha256:b7458ef93f605b9d46a4bf3a8dc1755dad1f31d030c8679edf304e343b347eea
     # via -r requirements.in
-gcp-releasetool==1.16.0 \
-    --hash=sha256:27bf19d2e87aaa884096ff941aa3c592c482be3d6a2bfe6f06afafa6af2353e3 \
-    --hash=sha256:a316b197a543fd036209d0caba7a8eb4d236d8e65381c80cbc6d7efaa7606d63
+gcp-releasetool==2.0.0 \
+    --hash=sha256:3d73480b50ba243f22d7c7ec08b115a30e1c7817c4899781840c26f9c55b8277 \
+    --hash=sha256:7aa9fd935ec61e581eb8458ad00823786d91756c25e492f372b2b30962f3c28f
     # via -r requirements.in
 google-api-core==2.12.0 \
     --hash=sha256:c22e01b1e3c4dcd90998494879612c38d0a3411d1f7b679eb89e2abe3ce1f553 \
@@ -242,9 +252,9 @@ googleapis-common-protos==1.61.0 \
     --hash=sha256:22f1915393bb3245343f6efe87f6fe868532efc12aa26b391b15132e1279f1c0 \
     --hash=sha256:8a64866a97f6304a7179873a465d6eee97b7a24ec6cfd78e0f575e96b821240b
     # via google-api-core
-idna==3.4 \
-    --hash=sha256:814f528e8dead7d329833b91c5faa87d60bf71824cd12a7530b5526063d02cb4 \
-    --hash=sha256:90b77e79eaa3eba6de819a0c442c0b4ceefc341a7a2ab77d7562bf49f425c5c2
+idna==3.7 \
+    --hash=sha256:028ff3aadf0609c1fd278d8ea3089299412a7a8b9bd005dd08b9f8285bcb5cfc \
+    --hash=sha256:82fee1fc78add43492d3a1898bfa6d8a904cc97d8427f683ed8e798d07761aa0
     # via requests
 importlib-metadata==6.8.0 \
     --hash=sha256:3ebb78df84a805d7698245025b975d9d67053cd94c79245ba4b3eb694abe68bb \
@@ -263,9 +273,9 @@ jeepney==0.8.0 \
     # via
     #   keyring
     #   secretstorage
-jinja2==3.1.2 \
-    --hash=sha256:31351a702a408a9e7595a8fc6150fc3f43bb6bf7e319770cbc0db9df9437e852 \
-    --hash=sha256:6088930bfe239f0e6710546ab9c19c9ef35e29792895fed6e6e31a023a182a61
+jinja2==3.1.3 \
+    --hash=sha256:7d6d50dd97d52cbc355597bd845fabfbac3f551e1f99619e39a35ce8c370b5fa \
+    --hash=sha256:ac8bd6544d4bb2c9792bf3a159e80bba8fda7f07e81bc3aed565432d5925ba90
     # via gcp-releasetool
 keyring==24.2.0 \
     --hash=sha256:4901caaf597bfd3bbd78c9a0c7c4c29fcd8310dab2cffefe749e916b6527acd6 \
@@ -383,29 +393,18 @@ platformdirs==3.11.0 \
     --hash=sha256:cf8ee52a3afdb965072dcc652433e0c7e3e40cf5ea1477cd4b3b1d2eb75495b3 \
     --hash=sha256:e9d171d00af68be50e9202731309c4e658fd8bc76f55c11c7dd760d023bda68e
     # via virtualenv
-protobuf==3.20.3 \
-    --hash=sha256:03038ac1cfbc41aa21f6afcbcd357281d7521b4157926f30ebecc8d4ea59dcb7 \
-    --hash=sha256:28545383d61f55b57cf4df63eebd9827754fd2dc25f80c5253f9184235db242c \
-    --hash=sha256:2e3427429c9cffebf259491be0af70189607f365c2f41c7c3764af6f337105f2 \
-    --hash=sha256:398a9e0c3eaceb34ec1aee71894ca3299605fa8e761544934378bbc6c97de23b \
-    --hash=sha256:44246bab5dd4b7fbd3c0c80b6f16686808fab0e4aca819ade6e8d294a29c7050 \
-    --hash=sha256:447d43819997825d4e71bf5769d869b968ce96848b6479397e29fc24c4a5dfe9 \
-    --hash=sha256:67a3598f0a2dcbc58d02dd1928544e7d88f764b47d4a286202913f0b2801c2e7 \
-    --hash=sha256:74480f79a023f90dc6e18febbf7b8bac7508420f2006fabd512013c0c238f454 \
-    --hash=sha256:819559cafa1a373b7096a482b504ae8a857c89593cf3a25af743ac9ecbd23480 \
-    --hash=sha256:899dc660cd599d7352d6f10d83c95df430a38b410c1b66b407a6b29265d66469 \
-    --hash=sha256:8c0c984a1b8fef4086329ff8dd19ac77576b384079247c770f29cc8ce3afa06c \
-    --hash=sha256:9aae4406ea63d825636cc11ffb34ad3379335803216ee3a856787bcf5ccc751e \
-    --hash=sha256:a7ca6d488aa8ff7f329d4c545b2dbad8ac31464f1d8b1c87ad1346717731e4db \
-    --hash=sha256:b6cc7ba72a8850621bfec987cb72623e703b7fe2b9127a161ce61e61558ad905 \
-    --hash=sha256:bf01b5720be110540be4286e791db73f84a2b721072a3711efff6c324cdf074b \
-    --hash=sha256:c02ce36ec760252242a33967d51c289fd0e1c0e6e5cc9397e2279177716add86 \
-    --hash=sha256:d9e4432ff660d67d775c66ac42a67cf2453c27cb4d738fc22cb53b5d84c135d4 \
-    --hash=sha256:daa564862dd0d39c00f8086f88700fdbe8bc717e993a21e90711acfed02f2402 \
-    --hash=sha256:de78575669dddf6099a8a0f46a27e82a1783c557ccc38ee620ed8cc96d3be7d7 \
-    --hash=sha256:e64857f395505ebf3d2569935506ae0dfc4a15cb80dc25261176c784662cdcc4 \
-    --hash=sha256:f4bd856d702e5b0d96a00ec6b307b0f51c1982c2bf9c0052cf9019e9a544ba99 \
-    --hash=sha256:f4c42102bc82a51108e449cbb32b19b180022941c727bac0cfd50170341f16ee
+protobuf==4.25.3 \
+    --hash=sha256:19b270aeaa0099f16d3ca02628546b8baefe2955bbe23224aaf856134eccf1e4 \
+    --hash=sha256:209ba4cc916bab46f64e56b85b090607a676f66b473e6b762e6f1d9d591eb2e8 \
+    --hash=sha256:25b5d0b42fd000320bd7830b349e3b696435f3b329810427a6bcce6a5492cc5c \
+    --hash=sha256:7c8daa26095f82482307bc717364e7c13f4f1c99659be82890dcfc215194554d \
+    --hash=sha256:c053062984e61144385022e53678fbded7aea14ebb3e0305ae3592fb219ccfa4 \
+    --hash=sha256:d4198877797a83cbfe9bffa3803602bbe1625dc30d8a097365dbc762e5790faa \
+    --hash=sha256:e3c97a1555fd6388f857770ff8b9703083de6bf1f9274a002a332d65fbb56c8c \
+    --hash=sha256:e7cb0ae90dd83727f0c0718634ed56837bfeeee29a5f82a7514c03ee1364c019 \
+    --hash=sha256:f0700d54bcf45424477e46a9f0944155b46fb0639d69728739c0e47bab83f2b9 \
+    --hash=sha256:f1279ab38ecbfae7e456a108c5c0681e4956d5b1090027c1de0f934dfdb4b35c \
+    --hash=sha256:f4f118245c4a087776e0a8408be33cf09f6c547442c00395fbfb116fac2f8ac2
     # via
     #   gcp-docuploader
     #   gcp-releasetool
@@ -509,7 +508,7 @@ zipp==3.17.0 \
     # via importlib-metadata
 
 # The following packages are considered to be unsafe in a requirements file:
-setuptools==68.2.2 \
-    --hash=sha256:4ac1475276d2f1c48684874089fefcd83bd7162ddaafb81fac866ba0db282a87 \
-    --hash=sha256:b454a35605876da60632df1a60f736524eb73cc47bbc9f3f1ef1b644de74fd2a
+setuptools==69.2.0 \
+    --hash=sha256:0ff4183f8f42cd8fa3acea16c45205521a4ef28f73c6391d8a25e92893134f2e \
+    --hash=sha256:c21c49fb1042386df081cb5d86759792ab89efca84cf114889191cd09aacc80c
     # via -r requirements.in
diff --git a/.readthedocs.yml b/.readthedocs.yml
index ebea21ff..309b5e76 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -3,4 +3,4 @@ build:
   image: latest
 python:
   pip_install: true
-  version: 3.6
+  version: 3.9
diff --git a/.repo-metadata.json b/.repo-metadata.json
index 477f07c7..cbe8a78e 100644
--- a/.repo-metadata.json
+++ b/.repo-metadata.json
@@ -6,7 +6,7 @@
     "language": "python",
     "library_type": "CORE",
     "repo": "googleapis/proto-plus-python",
-    "distribution_name": "proto-plus-python",
+    "distribution_name": "proto-plus",
     "default_version": "",
     "codeowner_team": ""
 }
diff --git a/CHANGELOG.md b/CHANGELOG.md
index a22bc063..2171e424 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,25 @@
 # Changelog
 
+## [1.24.0](https://github.com/googleapis/proto-plus-python/compare/v1.23.0...v1.24.0) (2024-06-11)
+
+
+### Features
+
+* Add `always_print_fields_with_no_presence` fields to `to_json` and `to_dict` ([0f89372](https://github.com/googleapis/proto-plus-python/commit/0f893724cabe513a5a9f9c8428dbd31f1b4f1d52))
+
+
+### Bug Fixes
+
+* Add compatibility with protobuf==5.x ([0f89372](https://github.com/googleapis/proto-plus-python/commit/0f893724cabe513a5a9f9c8428dbd31f1b4f1d52))
+* AttributeError module 'google._upb._message' has no attribute 'MessageMapContainer' ([0f89372](https://github.com/googleapis/proto-plus-python/commit/0f893724cabe513a5a9f9c8428dbd31f1b4f1d52))
+* **deps:** Allow protobuf 5.x ([#457](https://github.com/googleapis/proto-plus-python/issues/457)) ([62d74e3](https://github.com/googleapis/proto-plus-python/commit/62d74e3275476b82fed48f2119fc761fe2371292))
+* Drop python 3.6 ([#456](https://github.com/googleapis/proto-plus-python/issues/456)) ([5a7666c](https://github.com/googleapis/proto-plus-python/commit/5a7666c15002aee0fab44a9aa6d3279aab3f1f69))
+
+
+### Documentation
+
+* Deprecate field `including_default_value_fields` in `to_json` and `to_dict` ([0f89372](https://github.com/googleapis/proto-plus-python/commit/0f893724cabe513a5a9f9c8428dbd31f1b4f1d52))
+
 ## [1.23.0](https://github.com/googleapis/proto-plus-python/compare/v1.22.3...v1.23.0) (2023-12-01)
 
 
diff --git a/noxfile.py b/noxfile.py
index c6a850c2..19c80c95 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -13,23 +13,22 @@
 # limitations under the License.
 
 from __future__ import absolute_import
-import os
-import pathlib
 
 import nox
+import pathlib
 
 
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
 
 
 PYTHON_VERSIONS = [
-    "3.6",
     "3.7",
     "3.8",
     "3.9",
     "3.10",
     "3.11",
     "3.12",
+    "3.13",
 ]
 
 # Error if a python version is missing
@@ -37,26 +36,30 @@
 
 
 @nox.session(python=PYTHON_VERSIONS)
-def unit(session, proto="python"):
+@nox.parametrize("implementation", ["cpp", "upb", "python"])
+def unit(session, implementation):
     """Run the unit test suite."""
 
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
     )
 
-    session.env["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = proto
+    session.env["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = implementation
     session.install("coverage", "pytest", "pytest-cov", "pytz")
     session.install("-e", ".[testing]", "-c", constraints_path)
-    if proto == "cpp":  # 4.20 does not have cpp.
-        session.install("protobuf==3.19.0")
+    # TODO(https://github.com/googleapis/proto-plus-python/issues/389):
+    # Remove the 'cpp' implementation once support for Protobuf 3.x is dropped.
+    # The 'cpp' implementation requires Protobuf<4.
+    if implementation == "cpp":
+        session.install("protobuf<4")
 
     # TODO(https://github.com/googleapis/proto-plus-python/issues/403): re-enable `-W=error`
     # The warnings-as-errors flag `-W=error` was removed in
     # https://github.com/googleapis/proto-plus-python/pull/400.
     # It should be re-added once issue
-    # https://github.com/protocolbuffers/protobuf/issues/12186 is fixed.
+    # https://github.com/protocolbuffers/protobuf/issues/15077 is fixed.
     session.run(
-        "py.test",
+        "pytest",
         "--quiet",
         *(
             session.posargs  # Coverage info when running individual tests is annoying.
@@ -71,24 +74,78 @@ def unit(session, proto="python"):
     )
 
 
-# Check if protobuf has released wheels for new python versions
-# https://pypi.org/project/protobuf/#files
-# This list will generally be shorter than 'unit'
-@nox.session(python=["3.6", "3.7", "3.8", "3.9", "3.10"])
-def unitcpp(session):
-    return unit(session, proto="cpp")
+# Only test upb and python implementation backends.
+# As of protobuf 4.x, the "ccp" implementation is not available in the PyPI package as per
+# https://github.com/protocolbuffers/protobuf/tree/main/python#implementation-backends
+@nox.session(python=PYTHON_VERSIONS[-2])
+@nox.parametrize("implementation", ["python", "upb"])
+def prerelease_deps(session, implementation):
+    """Run the unit test suite against pre-release versions of dependencies."""
 
+    session.env["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = implementation
 
-@nox.session(python=PYTHON_VERSIONS)
-def unitupb(session):
-    return unit(session, proto="upb")
+    # Install test environment dependencies
+    session.install("coverage", "pytest", "pytest-cov", "pytz")
+
+    # Install the package without dependencies
+    session.install("-e", ".", "--no-deps")
+
+    prerel_deps = [
+        "google-api-core",
+        # dependency of google-api-core
+        "googleapis-common-protos",
+    ]
+
+    for dep in prerel_deps:
+        session.install("--pre", "--no-deps", "--upgrade", dep)
+
+    session.install("--pre", "--upgrade", "protobuf")
+    # Print out prerelease package versions
+    session.run(
+        "python", "-c", "import google.protobuf; print(google.protobuf.__version__)"
+    )
+    session.run(
+        "python", "-c", "import google.api_core; print(google.api_core.__version__)"
+    )
+
+    # TODO(https://github.com/googleapis/proto-plus-python/issues/403): re-enable `-W=error`
+    # The warnings-as-errors flag `-W=error` was removed in
+    # https://github.com/googleapis/proto-plus-python/pull/400.
+    # It should be re-added once issue
+    # https://github.com/protocolbuffers/protobuf/issues/15077 is fixed.
+    session.run(
+        "pytest",
+        "--quiet",
+        *(
+            session.posargs  # Coverage info when running individual tests is annoying.
+            or [
+                "--cov=proto",
+                "--cov-config=.coveragerc",
+                "--cov-report=term",
+                "--cov-report=html",
+                "tests",
+            ]
+        ),
+    )
 
 
 @nox.session(python="3.9")
 def docs(session):
     """Build the docs."""
 
-    session.install("sphinx==4.2.0", "sphinx_rtd_theme")
+    session.install(
+        # We need to pin to specific versions of the `sphinxcontrib-*` packages
+        # which still support sphinx 4.x.
+        # See https://github.com/googleapis/sphinx-docfx-yaml/issues/344
+        # and https://github.com/googleapis/sphinx-docfx-yaml/issues/345.
+        "sphinxcontrib-applehelp==1.0.4",
+        "sphinxcontrib-devhelp==1.0.2",
+        "sphinxcontrib-htmlhelp==2.0.1",
+        "sphinxcontrib-qthelp==1.0.3",
+        "sphinxcontrib-serializinghtml==1.1.5",
+        "sphinx==4.5.0",
+        "sphinx_rtd_theme",
+    )
     session.install(".")
 
     # Build the docs!
diff --git a/proto/marshal/compat.py b/proto/marshal/compat.py
index e10999bb..dc77f3ac 100644
--- a/proto/marshal/compat.py
+++ b/proto/marshal/compat.py
@@ -19,6 +19,9 @@
 # not be included.
 
 from google.protobuf.internal import containers
+import google.protobuf
+
+PROTOBUF_VERSION = google.protobuf.__version__
 
 # Import protobuf 4.xx first and fallback to earlier version
 # if not present.
@@ -37,14 +40,28 @@
 repeated_scalar_types = (containers.RepeatedScalarFieldContainer,)
 map_composite_types = (containers.MessageMap,)
 
+# In `proto/marshal.py`, for compatibility with protobuf 5.x,
+# we'll use `map_composite_type_names` to check whether
+# the name of the class of a protobuf type is
+# `MessageMapContainer`, and, if `True`, return a MapComposite.
+# See https://github.com/protocolbuffers/protobuf/issues/16596
+map_composite_type_names = ("MessageMapContainer",)
+
 if _message:
     repeated_composite_types += (_message.RepeatedCompositeContainer,)
     repeated_scalar_types += (_message.RepeatedScalarContainer,)
-    map_composite_types += (_message.MessageMapContainer,)
 
+    # In `proto/marshal.py`, for compatibility with protobuf 5.x,
+    # we'll use `map_composite_type_names` to check whether
+    # the name of the class of a protobuf type is
+    # `MessageMapContainer`, and, if `True`, return a MapComposite.
+    # See https://github.com/protocolbuffers/protobuf/issues/16596
+    if PROTOBUF_VERSION[0:2] in ["3.", "4."]:
+        map_composite_types += (_message.MessageMapContainer,)
 
 __all__ = (
     "repeated_composite_types",
     "repeated_scalar_types",
     "map_composite_types",
+    "map_composite_type_names",
 )
diff --git a/proto/marshal/marshal.py b/proto/marshal/marshal.py
index e9fbbb9f..d278421a 100644
--- a/proto/marshal/marshal.py
+++ b/proto/marshal/marshal.py
@@ -188,7 +188,14 @@ def to_python(self, proto_type, value, *, absent: bool = None):
                 return Repeated(value, marshal=self)
 
         # Same thing for maps of messages.
-        if value_type in compat.map_composite_types:
+        # See https://github.com/protocolbuffers/protobuf/issues/16596
+        # We need to look up the name of the type in compat.map_composite_type_names
+        # as class `MessageMapContainer` is no longer exposed
+        # This is done to avoid taking a breaking change in proto-plus.
+        if (
+            value_type in compat.map_composite_types
+            or value_type.__name__ in compat.map_composite_type_names
+        ):
             return MapComposite(value, marshal=self)
         return self.get_rule(proto_type=proto_type).to_python(value, absent=absent)
 
diff --git a/proto/message.py b/proto/message.py
index 7232d42f..2772fb42 100644
--- a/proto/message.py
+++ b/proto/message.py
@@ -16,8 +16,10 @@
 import collections.abc
 import copy
 import re
-from typing import List, Type
+from typing import List, Optional, Type
+import warnings
 
+import google.protobuf
 from google.protobuf import descriptor_pb2
 from google.protobuf import message
 from google.protobuf.json_format import MessageToDict, MessageToJson, Parse
@@ -32,6 +34,8 @@
 from proto.utils import has_upb
 
 
+PROTOBUF_VERSION = google.protobuf.__version__
+
 _upb = has_upb()  # Important to cache result here.
 
 
@@ -369,16 +373,101 @@ def deserialize(cls, payload: bytes) -> "Message":
         """
         return cls.wrap(cls.pb().FromString(payload))
 
+    def _warn_if_including_default_value_fields_is_used_protobuf_5(
+        cls, including_default_value_fields: Optional[bool]
+    ) -> None:
+        """
+        Warn Protobuf 5.x+ users that `including_default_value_fields` is deprecated if it is set.
+
+        Args:
+            including_default_value_fields (Optional(bool)): The value of `including_default_value_fields` set by the user.
+        """
+        if (
+            PROTOBUF_VERSION[0] not in ("3", "4")
+            and including_default_value_fields is not None
+        ):
+            warnings.warn(
+                """The argument `including_default_value_fields` has been removed from
+                Protobuf 5.x. Please use `always_print_fields_with_no_presence` instead.
+                """,
+                DeprecationWarning,
+            )
+
+    def _raise_if_print_fields_values_are_set_and_differ(
+        cls,
+        always_print_fields_with_no_presence: Optional[bool],
+        including_default_value_fields: Optional[bool],
+    ) -> None:
+        """
+        Raise Exception if both `always_print_fields_with_no_presence` and `including_default_value_fields` are set
+            and the values differ.
+
+        Args:
+            always_print_fields_with_no_presence (Optional(bool)): The value of `always_print_fields_with_no_presence` set by the user.
+            including_default_value_fields (Optional(bool)): The value of `including_default_value_fields` set by the user.
+        Returns:
+            None
+        Raises:
+            ValueError: if both `always_print_fields_with_no_presence` and `including_default_value_fields` are set and
+                the values differ.
+        """
+        if (
+            always_print_fields_with_no_presence is not None
+            and including_default_value_fields is not None
+            and always_print_fields_with_no_presence != including_default_value_fields
+        ):
+            raise ValueError(
+                "Arguments `always_print_fields_with_no_presence` and `including_default_value_fields` must match"
+            )
+
+    def _normalize_print_fields_without_presence(
+        cls,
+        always_print_fields_with_no_presence: Optional[bool],
+        including_default_value_fields: Optional[bool],
+    ) -> bool:
+        """
+        Return true if fields with no presence should be included in the results.
+        By default, fields with no presence will be included in the results
+        when both `always_print_fields_with_no_presence` and
+        `including_default_value_fields` are not set
+
+        Args:
+            always_print_fields_with_no_presence (Optional(bool)): The value of `always_print_fields_with_no_presence` set by the user.
+            including_default_value_fields (Optional(bool)): The value of `including_default_value_fields` set by the user.
+        Returns:
+            None
+        Raises:
+            ValueError: if both `always_print_fields_with_no_presence` and `including_default_value_fields` are set and
+                the values differ.
+        """
+
+        cls._warn_if_including_default_value_fields_is_used_protobuf_5(
+            including_default_value_fields
+        )
+        cls._raise_if_print_fields_values_are_set_and_differ(
+            always_print_fields_with_no_presence, including_default_value_fields
+        )
+        # Default to True if neither `always_print_fields_with_no_presence` or `including_default_value_fields` is set
+        return (
+            (
+                always_print_fields_with_no_presence is None
+                and including_default_value_fields is None
+            )
+            or always_print_fields_with_no_presence
+            or including_default_value_fields
+        )
+
     def to_json(
         cls,
         instance,
         *,
         use_integers_for_enums=True,
-        including_default_value_fields=True,
+        including_default_value_fields=None,
         preserving_proto_field_name=False,
         sort_keys=False,
         indent=2,
         float_precision=None,
+        always_print_fields_with_no_presence=None,
     ) -> str:
         """Given a message instance, serialize it to json
 
@@ -388,6 +477,11 @@ def to_json(
             use_integers_for_enums (Optional(bool)): An option that determines whether enum
                 values should be represented by strings (False) or integers (True).
                 Default is True.
+            including_default_value_fields (Optional(bool)): Deprecated. Use argument
+                `always_print_fields_with_no_presence` instead. An option that
+                determines whether the default field values should be included in the results.
+                This value must match `always_print_fields_with_no_presence`,
+                if both arguments are explictly set.
             preserving_proto_field_name (Optional(bool)): An option that
                 determines whether field name representations preserve
                 proto case (snake_case) or use lowerCamelCase. Default is False.
@@ -398,19 +492,46 @@ def to_json(
                 Pass None for the most compact representation without newlines.
             float_precision (Optional(int)): If set, use this to specify float field valid digits.
                 Default is None.
+            always_print_fields_with_no_presence (Optional(bool)): If True, fields without
+                presence (implicit presence scalars, repeated fields, and map fields) will
+                always be serialized. Any field that supports presence is not affected by
+                this option (including singular message fields and oneof fields).
+                This value must match `including_default_value_fields`,
+                if both arguments are explictly set.
         Returns:
             str: The json string representation of the protocol buffer.
         """
-        return MessageToJson(
-            cls.pb(instance),
-            use_integers_for_enums=use_integers_for_enums,
-            including_default_value_fields=including_default_value_fields,
-            preserving_proto_field_name=preserving_proto_field_name,
-            sort_keys=sort_keys,
-            indent=indent,
-            float_precision=float_precision,
+
+        print_fields = cls._normalize_print_fields_without_presence(
+            always_print_fields_with_no_presence, including_default_value_fields
         )
 
+        if PROTOBUF_VERSION[0] in ("3", "4"):
+            return MessageToJson(
+                cls.pb(instance),
+                use_integers_for_enums=use_integers_for_enums,
+                including_default_value_fields=print_fields,
+                preserving_proto_field_name=preserving_proto_field_name,
+                sort_keys=sort_keys,
+                indent=indent,
+                float_precision=float_precision,
+            )
+        else:
+            # The `including_default_value_fields` argument was removed from protobuf 5.x
+            # and replaced with `always_print_fields_with_no_presence` which very similar but has
+            # handles optional fields consistently by not affecting them.
+            # The old flag accidentally had inconsistent behavior between proto2
+            # optional and proto3 optional fields.
+            return MessageToJson(
+                cls.pb(instance),
+                use_integers_for_enums=use_integers_for_enums,
+                always_print_fields_with_no_presence=print_fields,
+                preserving_proto_field_name=preserving_proto_field_name,
+                sort_keys=sort_keys,
+                indent=indent,
+                float_precision=float_precision,
+            )
+
     def from_json(cls, payload, *, ignore_unknown_fields=False) -> "Message":
         """Given a json string representing an instance,
         parse it into a message.
@@ -434,39 +555,66 @@ def to_dict(
         *,
         use_integers_for_enums=True,
         preserving_proto_field_name=True,
-        including_default_value_fields=True,
+        including_default_value_fields=None,
         float_precision=None,
+        always_print_fields_with_no_presence=None,
     ) -> "Message":
         """Given a message instance, return its representation as a python dict.
 
         Args:
             instance: An instance of this message type, or something
-                      compatible (accepted by the type's constructor).
+                compatible (accepted by the type's constructor).
             use_integers_for_enums (Optional(bool)): An option that determines whether enum
                 values should be represented by strings (False) or integers (True).
                 Default is True.
             preserving_proto_field_name (Optional(bool)): An option that
                 determines whether field name representations preserve
                 proto case (snake_case) or use lowerCamelCase. Default is True.
-            including_default_value_fields (Optional(bool)): An option that
+            including_default_value_fields (Optional(bool)): Deprecated. Use argument
+                `always_print_fields_with_no_presence` instead. An option that
                 determines whether the default field values should be included in the results.
-                Default is True.
+                This value must match `always_print_fields_with_no_presence`,
+                if both arguments are explictly set.
             float_precision (Optional(int)): If set, use this to specify float field valid digits.
                 Default is None.
+            always_print_fields_with_no_presence (Optional(bool)): If True, fields without
+                presence (implicit presence scalars, repeated fields, and map fields) will
+                always be serialized. Any field that supports presence is not affected by
+                this option (including singular message fields and oneof fields). This value
+                must match `including_default_value_fields`, if both arguments are explictly set.
 
         Returns:
             dict: A representation of the protocol buffer using pythonic data structures.
                   Messages and map fields are represented as dicts,
                   repeated fields are represented as lists.
         """
-        return MessageToDict(
-            cls.pb(instance),
-            including_default_value_fields=including_default_value_fields,
-            preserving_proto_field_name=preserving_proto_field_name,
-            use_integers_for_enums=use_integers_for_enums,
-            float_precision=float_precision,
+
+        print_fields = cls._normalize_print_fields_without_presence(
+            always_print_fields_with_no_presence, including_default_value_fields
         )
 
+        if PROTOBUF_VERSION[0] in ("3", "4"):
+            return MessageToDict(
+                cls.pb(instance),
+                including_default_value_fields=print_fields,
+                preserving_proto_field_name=preserving_proto_field_name,
+                use_integers_for_enums=use_integers_for_enums,
+                float_precision=float_precision,
+            )
+        else:
+            # The `including_default_value_fields` argument was removed from protobuf 5.x
+            # and replaced with `always_print_fields_with_no_presence` which very similar but has
+            # handles optional fields consistently by not affecting them.
+            # The old flag accidentally had inconsistent behavior between proto2
+            # optional and proto3 optional fields.
+            return MessageToDict(
+                cls.pb(instance),
+                always_print_fields_with_no_presence=print_fields,
+                preserving_proto_field_name=preserving_proto_field_name,
+                use_integers_for_enums=use_integers_for_enums,
+                float_precision=float_precision,
+            )
+
     def copy_from(cls, instance, other):
         """Equivalent for protobuf.Message.CopyFrom
 
diff --git a/proto/version.py b/proto/version.py
index f11d15fb..dbdc76e0 100644
--- a/proto/version.py
+++ b/proto/version.py
@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-__version__ = "1.23.0"
+__version__ = "1.24.0"
diff --git a/pytest.ini b/pytest.ini
index 985c2559..ba89114a 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -4,3 +4,5 @@ filterwarnings =
     error
     # Remove once https://github.com/protocolbuffers/protobuf/issues/12186 is fixed
     ignore:.*custom tp_new.*in Python 3.14:DeprecationWarning
+    # Remove once deprecated field `including_default_value_fields` is removed
+    ignore:.*The argument `including_default_value_fields` has been removed.*:DeprecationWarning
diff --git a/setup.py b/setup.py
index 796f0a91..e3a54892 100644
--- a/setup.py
+++ b/setup.py
@@ -42,13 +42,13 @@
     long_description=README,
     platforms="Posix; MacOS X",
     include_package_data=True,
-    install_requires=("protobuf >= 3.19.0, <5.0.0dev",),
+    install_requires=("protobuf >=3.19.0, <6.0.0dev",),
     extras_require={
         "testing": [
-            "google-api-core[grpc] >= 1.31.5",
+            "google-api-core >= 1.31.5",
         ],
     },
-    python_requires=">=3.6",
+    python_requires=">=3.7",
     classifiers=[
         "Development Status :: 5 - Production/Stable",
         "Environment :: Console",
@@ -56,7 +56,6 @@
         "License :: OSI Approved :: Apache Software License",
         "Operating System :: POSIX",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
diff --git a/testing/constraints-3.13.txt b/testing/constraints-3.13.txt
new file mode 100644
index 00000000..e69de29b
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
deleted file mode 100644
index 849c8e7c..00000000
--- a/testing/constraints-3.6.txt
+++ /dev/null
@@ -1,9 +0,0 @@
-# This constraints file is used to check that lower bounds
-# are correct in setup.py
-# List *all* library dependencies and extras in this file.
-# Pin the version to the lower bound.
-#
-# e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
-# Then this file should have foo==1.14.0
-google-api-core==1.31.5
-protobuf==3.19.0
diff --git a/tests/conftest.py b/tests/conftest.py
index 765326c6..9f2f5c95 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -41,9 +41,11 @@ def pytest_runtest_setup(item):
 
         item._mocks.append(
             mock.patch(
-                "google._upb._message.default_pool"
-                if has_upb()
-                else "google.protobuf.pyext._message.default_pool",
+                (
+                    "google._upb._message.default_pool"
+                    if has_upb()
+                    else "google.protobuf.pyext._message.default_pool"
+                ),
                 pool,
             )
         )
@@ -67,6 +69,14 @@ def pytest_runtest_setup(item):
     for name in dir(item.module):
         if name.endswith("_pb2") and not name.startswith("test_"):
             module = getattr(item.module, name)
+
+            # Exclude `google.protobuf.descriptor_pb2` which causes error
+            # `RecursionError: maximum recursion depth exceeded while calling a Python object`
+            # when running the test suite and is not required for tests.
+            # See https://github.com/googleapis/proto-plus-python/issues/425
+            if module.__package__ == "google.protobuf" and name == "descriptor_pb2":
+                continue
+
             pool.AddSerializedFile(module.DESCRIPTOR.serialized_pb)
             fd = pool.FindFileByName(module.DESCRIPTOR.name)
 
diff --git a/tests/test_json.py b/tests/test_json.py
index e94e935a..ae3cf59e 100644
--- a/tests/test_json.py
+++ b/tests/test_json.py
@@ -121,10 +121,77 @@ class Squid(proto.Message):
     )
     assert json1 == '{"name":"Steve"}'
 
-    json2 = Squid.to_json(s).replace(" ", "").replace("\n", "")
-    assert (
-        json2 == '{"name":"Steve","massKg":0}' or json2 == '{"massKg":0,"name":"Steve"}'
+    json1 = (
+        Squid.to_json(s, always_print_fields_with_no_presence=False)
+        .replace(" ", "")
+        .replace("\n", "")
     )
+    assert json1 == '{"name":"Steve"}'
+
+    json1 = (
+        Squid.to_json(
+            s,
+            including_default_value_fields=False,
+            always_print_fields_with_no_presence=False,
+        )
+        .replace(" ", "")
+        .replace("\n", "")
+    )
+    assert json1 == '{"name":"Steve"}'
+
+    with pytest.raises(
+        ValueError,
+        match="Arguments.*always_print_fields_with_no_presence.*including_default_value_fields.*must match",
+    ):
+        Squid.to_json(
+            s,
+            including_default_value_fields=True,
+            always_print_fields_with_no_presence=False,
+        ).replace(" ", "").replace("\n", "")
+
+    with pytest.raises(
+        ValueError,
+        match="Arguments.*always_print_fields_with_no_presence.*including_default_value_fields.*must match",
+    ):
+        Squid.to_json(
+            s,
+            including_default_value_fields=False,
+            always_print_fields_with_no_presence=True,
+        ).replace(" ", "").replace("\n", "")
+
+    json2 = (
+        Squid.to_json(
+            s,
+            including_default_value_fields=True,
+            always_print_fields_with_no_presence=True,
+        )
+        .replace(" ", "")
+        .replace("\n", "")
+    )
+    assert json2 == '{"name":"Steve","massKg":0}'
+
+    json2 = (
+        Squid.to_json(
+            s,
+            including_default_value_fields=True,
+        )
+        .replace(" ", "")
+        .replace("\n", "")
+    )
+    assert json2 == '{"name":"Steve","massKg":0}'
+
+    json2 = (
+        Squid.to_json(
+            s,
+            always_print_fields_with_no_presence=True,
+        )
+        .replace(" ", "")
+        .replace("\n", "")
+    )
+    assert json2 == '{"name":"Steve","massKg":0}'
+
+    json2 = Squid.to_json(s).replace(" ", "").replace("\n", "")
+    assert json2 == '{"name":"Steve","massKg":0}'
 
     s1 = Squid.from_json(json1)
     s2 = Squid.from_json(json2)
diff --git a/tests/test_message.py b/tests/test_message.py
index 983cde82..720995a9 100644
--- a/tests/test_message.py
+++ b/tests/test_message.py
@@ -267,8 +267,63 @@ class Color(proto.Enum):
     expected_dict = {"mass_kg": 20}
     assert s_dict_2 == expected_dict
 
-    new_s = Squid(s_dict)
-    assert new_s == s
+    s_dict_2 = Squid.to_dict(s_new_2, always_print_fields_with_no_presence=False)
+    expected_dict = {"mass_kg": 20}
+    assert s_dict_2 == expected_dict
+
+    s_dict_2 = Squid.to_dict(
+        s_new_2,
+        including_default_value_fields=False,
+        always_print_fields_with_no_presence=False,
+    )
+    expected_dict = {"mass_kg": 20}
+    assert s_dict_2 == expected_dict
+
+    s_dict_2 = Squid.to_dict(
+        s_new_2,
+        including_default_value_fields=True,
+    )
+    expected_dict = {"mass_kg": 20, "chromatophores": []}
+    assert s_dict_2 == expected_dict
+
+    s_dict_2 = Squid.to_dict(
+        s_new_2,
+        always_print_fields_with_no_presence=True,
+    )
+    expected_dict = {"mass_kg": 20, "chromatophores": []}
+    assert s_dict_2 == expected_dict
+
+    s_dict_2 = Squid.to_dict(
+        s_new_2,
+        including_default_value_fields=True,
+        always_print_fields_with_no_presence=True,
+    )
+    expected_dict = {"mass_kg": 20, "chromatophores": []}
+    assert s_dict_2 == expected_dict
+
+    s_dict_2 = Squid.to_dict(s_new_2)
+    expected_dict = {"mass_kg": 20, "chromatophores": []}
+    assert s_dict_2 == expected_dict
+
+    with pytest.raises(
+        ValueError,
+        match="Arguments.*always_print_fields_with_no_presence.*including_default_value_fields.*must match",
+    ):
+        s_dict_2 = Squid.to_dict(
+            s_new_2,
+            including_default_value_fields=True,
+            always_print_fields_with_no_presence=False,
+        )
+
+    with pytest.raises(
+        ValueError,
+        match="Arguments.*always_print_fields_with_no_presence.*including_default_value_fields.*must match",
+    ):
+        s_dict_2 = Squid.to_dict(
+            s_new_2,
+            including_default_value_fields=False,
+            always_print_fields_with_no_presence=True,
+        )
 
 
 # TODO: https://github.com/googleapis/proto-plus-python/issues/390