diff --git a/.gitattributes b/.gitattributes
index 84c7add..14c3c35 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,4 +1,3 @@
 /Tests export-ignore
 /phpunit.xml.dist export-ignore
-/.gitattributes export-ignore
-/.gitignore export-ignore
+/.git* export-ignore
diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
new file mode 100644
index 0000000..4689c4d
--- /dev/null
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -0,0 +1,8 @@
+Please do not submit any Pull Requests here. They will be closed.
+---
+
+Please submit your PR here instead:
+https://github.com/symfony/symfony
+
+This repository is what we call a "subtree split": a read-only subset of that main repository.
+We're looking forward to your PR there!
diff --git a/.github/workflows/close-pull-request.yml b/.github/workflows/close-pull-request.yml
new file mode 100644
index 0000000..e55b478
--- /dev/null
+++ b/.github/workflows/close-pull-request.yml
@@ -0,0 +1,20 @@
+name: Close Pull Request
+
+on:
+  pull_request_target:
+    types: [opened]
+
+jobs:
+  run:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: superbrothers/close-pull-request@v3
+      with:
+        comment: |
+          Thanks for your Pull Request! We love contributions.
+
+          However, you should instead open your PR on the main repository:
+          https://github.com/symfony/symfony
+
+          This repository is what we call a "subtree split": a read-only subset of that main repository.
+          We're looking forward to your PR there!
diff --git a/Dotenv.php b/Dotenv.php
index d164aa0..0fa5bb6 100644
--- a/Dotenv.php
+++ b/Dotenv.php
@@ -495,7 +495,7 @@ private function resolveVariables(string $value, array $loadedVars): string
             (?!\()                             # no opening parenthesis
             (?P<opening_brace>\{)?             # optional brace
             (?P<name>'.self::VARNAME_REGEX.')? # var name
-            (?P<default_value>:[-=][^\}]++)?   # optional default value
+            (?P<default_value>:[-=][^\}]*+)?   # optional default value
             (?P<closing_brace>\})?             # optional closing brace
         /x';
 
diff --git a/Tests/DotenvTest.php b/Tests/DotenvTest.php
index 8ba0230..7f8bd27 100644
--- a/Tests/DotenvTest.php
+++ b/Tests/DotenvTest.php
@@ -175,6 +175,14 @@ public static function getEnvData()
             ["FOO=BAR\nBAR=\${NOTDEFINED:=TEST}", ['FOO' => 'BAR', 'NOTDEFINED' => 'TEST', 'BAR' => 'TEST']],
             ["FOO=\nBAR=\${FOO:=TEST}", ['FOO' => 'TEST', 'BAR' => 'TEST']],
             ["FOO=\nBAR=\$FOO:=TEST}", ['FOO' => 'TEST', 'BAR' => 'TEST}']],
+            ["FOO=BAR\nBAR=\${FOO:-}", ['FOO' => 'BAR', 'BAR' => 'BAR']],
+            ["FOO=BAR\nBAR=\${NOTDEFINED:-}", ['FOO' => 'BAR', 'BAR' => '']],
+            ["FOO=\nBAR=\${FOO:-}", ['FOO' => '', 'BAR' => '']],
+            ["FOO=\nBAR=\$FOO:-}", ['FOO' => '', 'BAR' => '}']],
+            ["FOO=BAR\nBAR=\${FOO:=}", ['FOO' => 'BAR', 'BAR' => 'BAR']],
+            ["FOO=BAR\nBAR=\${NOTDEFINED:=}", ['FOO' => 'BAR', 'NOTDEFINED' => '', 'BAR' => '']],
+            ["FOO=\nBAR=\${FOO:=}", ['FOO' => '', 'BAR' => '']],
+            ["FOO=\nBAR=\$FOO:=}", ['FOO' => '', 'BAR' => '}']],
             ["FOO=foo\nFOOBAR=\${FOO}\${BAR}", ['FOO' => 'foo', 'FOOBAR' => 'foo']],
 
             // underscores