diff --git a/diff-sha.sh b/diff-sha.sh
index 33a9a827..df6025e4 100644
--- a/diff-sha.sh
+++ b/diff-sha.sh
@@ -56,7 +56,7 @@ if [[ -z $GITHUB_BASE_REF ]]; then
     if [[ -z $INPUT_SHA ]]; then
       CURRENT_SHA=$(git rev-list --no-merges -n 1 HEAD 2>&1) && exit_status=$? || exit_status=$?
     else
-      git fetch --no-tags -u --progress --depth="$INPUT_FETCH_DEPTH" origin "$TARGET_BRANCH":"$TARGET_BRANCH"
+      git fetch --no-tags -u --progress --depth="$INPUT_FETCH_DEPTH" origin "$CURRENT_BRANCH":"$CURRENT_BRANCH"
       CURRENT_SHA=$INPUT_SHA; exit_status=$?
     fi
   fi