diff --git a/.github/workflows/pr.yaml b/.github/workflows/pr.yaml
index 53ec1d3..c085c4a 100644
--- a/.github/workflows/pr.yaml
+++ b/.github/workflows/pr.yaml
@@ -15,8 +15,10 @@ jobs:
       - name: Get changed files
         id: changed-files
         run: |
-          # Get the list of files that were changed between the base branch and the current commit
-          CHANGED_FILES=$(git diff --name-only origin/$GITHUB_BASE_REF...HEAD | grep "^packages/**")
+          # Get the merge base (common ancestor) of the PR
+          MERGE_BASE=$(git merge-base origin/${{ github.base_ref }} HEAD)
+          # only valid for PRs
+          CHANGED_FILES=$(git diff --name-only $MERGE_BASE | grep "^packages/**")
 
           if echo "$CHANGED_FILES"; then
             echo "any_changed=true" >> $GITHUB_OUTPUT