diff --git a/diff-sha.sh b/diff-sha.sh
index 167fe8a4..2c583f28 100644
--- a/diff-sha.sh
+++ b/diff-sha.sh
@@ -194,10 +194,14 @@ else
 
       if ! git rev-parse --quiet --verify "$PREVIOUS_SHA^{commit}" 1>/dev/null 2>&1; then
         # shellcheck disable=SC2046
-        PREVIOUS_SHA=$(git rev-parse $(git branch -r --sort=-committerdate | head -1) 2>&1) && exit_status=$? || exit_status=$?
+        PREVIOUS_SHA=$(git rev-parse origin/"$CURRENT_BRANCH" 2>&1) && exit_status=$? || exit_status=$?
       fi
     else
       PREVIOUS_SHA=$GITHUB_EVENT_PULL_REQUEST_BASE_SHA && exit_status=$? || exit_status=$?
+      
+      if ! git diff --name-only --ignore-submodules=all "$PREVIOUS_SHA"..."$CURRENT_SHA" 1>/dev/null 2>&1; then
+        PREVIOUS_SHA=$(git rev-parse origin/"$TARGET_BRANCH" 2>&1) && exit_status=$? || exit_status=$?
+      fi
     fi
 
     if [[ -z "$PREVIOUS_SHA" || "$PREVIOUS_SHA" == "$CURRENT_SHA" ]]; then