diff --git a/.github/workflows/branch-check-master.yml b/.github/workflows/branch-check-master.yml
new file mode 100644
index 0000000..92d2ad8
--- /dev/null
+++ b/.github/workflows/branch-check-master.yml
@@ -0,0 +1,17 @@
+name: Restrict merges to master
+
+on:
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  check-branch-master:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check if the source branch is preprod
+        run: |
+          if [ "${{ github.event.pull_request.head.ref }}" != "preprod" ]; then
+            echo "Pull requests to master must come from preprod branch."
+            exit 1
+          fi