diff --git a/.circleci/config.yml b/.circleci/config.yml
index ad663a7c5845..2f1a3e2339cf 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -103,7 +103,15 @@ commands:
     steps:
       - run:
           name: Install Matplotlib
-          command: python -m pip install --user -ve .
+          command: |
+            if [[ "$CIRCLE_BRANCH" == v*-doc ]]; then
+              # The v*-doc branches must build against the specified release.
+              version=${CIRCLE_BRANCH%-doc}
+              version=${version#v}
+              python -m pip install matplotlib==${version}
+            else
+              python -m pip install --user -ve .
+            fi
       - save_cache:
           key: build-deps-1
           paths:
diff --git a/.github/workflows/clean_pr.yml b/.github/workflows/clean_pr.yml
index fc2acc0b2e4c..f6c7e72e3fdc 100644
--- a/.github/workflows/clean_pr.yml
+++ b/.github/workflows/clean_pr.yml
@@ -20,3 +20,14 @@ jobs:
             exit 1
           fi
 
+      - name: Check for invalid backports to -doc branches
+        if: endsWith(github.base_ref, '-doc')
+        run: |
+          git fetch --quiet origin "$GITHUB_BASE_REF"
+          base="$(git merge-base "origin/$GITHUB_BASE_REF" 'HEAD^2')"
+          lib="$(git log "$base..HEAD^2" --pretty=tformat: --name-status -- lib src |
+                 cut --fields 2 | sort || true)"
+          if [[ -n "$lib" ]]; then
+            printf 'Changes to the following files have no effect and should not be backported:\n%s\n' "$lib"
+            exit 1
+          fi
diff --git a/lib/matplotlib/colors.py b/lib/matplotlib/colors.py
index c171ff6b99b3..da9d8187d143 100644
--- a/lib/matplotlib/colors.py
+++ b/lib/matplotlib/colors.py
@@ -8,8 +8,8 @@
 and for mapping numbers to colors in a 1-D array of colors called a colormap.
 
 Mapping data onto colors using a colormap typically involves two steps: a data
-array is first mapped onto the range 0-1 using a subclass of `Normalize`,
-then this number is mapped to a color using a subclass of `Colormap`.  Two
+array is first mapped onto the range 0-1 using a subclass of `Normalize`, then
+this number is mapped to a color using a subclass of `Colormap`.  Two
 subclasses of `Colormap` provided here:  `LinearSegmentedColormap`, which uses
 piecewise-linear interpolation to define colormaps, and `ListedColormap`, which
 makes a colormap from a list of colors.