diff --git a/diff-sha.sh b/diff-sha.sh
index cb05a568..98ed42bc 100644
--- a/diff-sha.sh
+++ b/diff-sha.sh
@@ -112,6 +112,8 @@ if [[ -z $GITHUB_BASE_REF ]]; then
       fi
     fi
   else
+    git fetch --no-tags -u --progress --depth="$INPUT_FETCH_DEPTH" origin "$TARGET_BRANCH":"$TARGET_BRANCH"
+
     PREVIOUS_SHA=$INPUT_BASE_SHA
     TARGET_BRANCH=$(git name-rev --name-only "$PREVIOUS_SHA" 2>&1) && exit_status=$? || exit_status=$?
     CURRENT_BRANCH=$TARGET_BRANCH