diff --git a/git-checkout-script b/git-checkout-script
index bf52e3bb24..48e1da9399 100755
--- a/git-checkout-script
+++ b/git-checkout-script
@@ -13,7 +13,7 @@ while [ "$#" != "0" ]; do
 		force=1
 		;;
 	*)
-		rev=$(git-rev-parse --verify --revs-only "$arg")
+		rev=$(git-rev-parse --verify --revs-only "$arg^0") || exit
 		if [ -z "$rev" ]; then
 			echo "unknown flag $arg"
 			exit 1