diff --git a/.github/workflows/auto-assign-milestone.yml b/.github/workflows/auto-assign-milestone.yml
index bdcfafb8b..03f72973d 100644
--- a/.github/workflows/auto-assign-milestone.yml
+++ b/.github/workflows/auto-assign-milestone.yml
@@ -7,6 +7,7 @@ on:
 jobs:
   assign_milestone:
     runs-on: ubuntu-latest
+    if: ${{ github.event.pull_request.head.repo.full_name == github.repository }}
     permissions:
       pull-requests: write
       issues: write