diff --git a/.github/workflows/pull.yml b/.github/workflows/pull.yml
index 02bde48b6..fcba84c41 100644
--- a/.github/workflows/pull.yml
+++ b/.github/workflows/pull.yml
@@ -88,7 +88,7 @@ jobs:
         # NUM:    5
       shell: bash
       run: |
-        RANGE=${BEFORE:-origin/master}..${GITHUB_HEAD_REF:+origin/$GITHUB_HEAD_REF}
+        RANGE=${BEFORE:-origin/master}..${GITHUB_HEAD_REF:-}
 
         echo "debug: last 10 commits:"
         echo "$(git log --format='%h -%d %s (%an, %ci)' -10)"