diff --git a/.github/workflows/build_and_test.yml b/.github/workflows/build_and_test.yml
index c1ec3f207b..6617ca42bb 100644
--- a/.github/workflows/build_and_test.yml
+++ b/.github/workflows/build_and_test.yml
@@ -120,6 +120,59 @@ jobs:
       - name: Run mypy to check types
         run: poetry run mypy .
 
+  # Check that the vendor/postgres-* submodules point to the
+  # corresponding REL_*_STABLE_neon branches.
+  check-submodules:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: true
+
+      - uses: dorny/paths-filter@v3
+        id: check-if-submodules-changed
+        with:
+          filters: |
+            vendor:
+              - 'vendor/**'
+
+      - name: Check vendor/postgres-v14 submodule reference
+        if: steps.check-if-submodules-changed.outputs.vendor == 'true'
+        uses: jtmullen/submodule-branch-check-action@v1
+        with:
+          path: "vendor/postgres-v14"
+          fetch_depth: "50"
+          sub_fetch_depth: "50"
+          pass_if_unchanged: true
+
+      - name: Check vendor/postgres-v15 submodule reference
+        if: steps.check-if-submodules-changed.outputs.vendor == 'true'
+        uses: jtmullen/submodule-branch-check-action@v1
+        with:
+          path: "vendor/postgres-v15"
+          fetch_depth: "50"
+          sub_fetch_depth: "50"
+          pass_if_unchanged: true
+
+      - name: Check vendor/postgres-v16 submodule reference
+        if: steps.check-if-submodules-changed.outputs.vendor == 'true'
+        uses: jtmullen/submodule-branch-check-action@v1
+        with:
+          path: "vendor/postgres-v16"
+          fetch_depth: "50"
+          sub_fetch_depth: "50"
+          pass_if_unchanged: true
+
+      - name: Check vendor/postgres-v17 submodule reference
+        if: steps.check-if-submodules-changed.outputs.vendor == 'true'
+        uses: jtmullen/submodule-branch-check-action@v1
+        with:
+          path: "vendor/postgres-v17"
+          fetch_depth: "50"
+          sub_fetch_depth: "50"
+          pass_if_unchanged: true
+
   check-codestyle-rust:
     needs: [ check-permissions, build-build-tools-image ]
     strategy:
@@ -1154,6 +1207,7 @@ jobs:
     # Usually we do `needs: [...]`
     needs:
       - build-and-test-locally
+      - check-submodules
       - check-codestyle-python
       - check-codestyle-rust
       - promote-images