diff --git a/.github/workflows/cooker-selfhosted.yml b/.github/workflows/cooker-selfhosted.yml
index ba1f8785..9ac31a7c 100644
--- a/.github/workflows/cooker-selfhosted.yml
+++ b/.github/workflows/cooker-selfhosted.yml
@@ -57,7 +57,7 @@ jobs:
           submodules: 'true'
 
       - name: Checkout PR branch (include changes)
-        if: ${{ github.event_name == 'pull_request' }}
+        if: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository }}
         run: |
           git fetch origin +refs/pull/${{ github.event.pull_request.number }}/merge
           git checkout -qf FETCH_HEAD