diff --git a/.github/workflows/commit-validation-pr.yml b/.github/workflows/commit-validation-pr.yml
new file mode 100644
index 000000000000..80311326cc18
--- /dev/null
+++ b/.github/workflows/commit-validation-pr.yml
@@ -0,0 +1,25 @@
+name: commit-validation-pr
+on: [pull_request]
+
+permissions:
+  contents: read
+
+jobs:
+  check-commit-msg-length:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+    - name: Check commit message length
+      run: |
+          git log ${{ github.event.pull_request.base.sha }}..${{ github.event.pull_request.head.sha }} | (
+            longlines=0
+            while IFS='' read -r line; do
+              if [ "${#line}" -gt 78 ]; then
+                echo "Overlong line: ${line}" >&2
+                longlines=$(( longlines + 1 ))
+              fi
+            done
+            [ "${longlines}" -eq 0 ]
+          )
diff --git a/.github/workflows/commit-validation.yml b/.github/workflows/commit-validation.yml
index 252e7bfdd865..46402f8630bd 100644
--- a/.github/workflows/commit-validation.yml
+++ b/.github/workflows/commit-validation.yml
@@ -1,5 +1,5 @@
 name: commit-validation
-on: [ push, pull_request ]
+on: [ push ]
 
 permissions:
   contents: read
@@ -16,8 +16,7 @@ jobs:
         result-encoding: json
         script: |
           var longlines = 0;
-          const pr = ${{ toJSON(github.event.pull_request) }};
-          const commits = (pr && pr.commits) || ${{ toJSON(github.event.commits) }};
+          const commits = ${{ toJSON(github.event.commits) }};
           for (const commit of commits) {
             for (const line of commit.message.split('\n')) {
               if (line.length > 78) {