diff --git a/diff-sha.sh b/diff-sha.sh
index f2bd7687..8dd0200c 100644
--- a/diff-sha.sh
+++ b/diff-sha.sh
@@ -178,10 +178,10 @@ else
   while ! git merge-base "$TARGET_BRANCH" "$CURRENT_BRANCH" > /dev/null; do
     depth=$((depth+1024))
     
-    if [[ -d .git/shallow ]]; then
-      git fetch -q --deepth=$depth --unshallow origin "$CURRENT_BRANCH":"$CURRENT_BRANCH"
+    if [[ -f .git/shallow ]]; then
+      git fetch -q --deepen=$depth origin "$CURRENT_BRANCH":"$CURRENT_BRANCH"
     else
-      git fetch -q --deepth=$depth origin "$CURRENT_BRANCH":"$CURRENT_BRANCH"
+      git fetch -q --depth=$depth origin "$CURRENT_BRANCH":"$CURRENT_BRANCH"
     fi
     
     if [[ $depth -gt 5000 ]]; then