1 files changed, 3 insertions, 0 deletions
diff --git a/git-rebase.sh b/git-rebase.sh
index 8a5f44aa5e..c1619ff140 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -6,6 +6,8 @@
 USAGE='<upstream> [<head>]'
 . git-sh-setup
 
+case $# in 1|2) ;; *) usage ;; esac
+
 # Make sure we do not have .dotest
 if mkdir .dotest
 then
@@ -37,6 +39,7 @@ esac
 # If the branch to rebase is given, first switch to it.
 case "$#" in
 2)
+	head=$(git-rev-parse --verify "$2^") || usage
 	git-checkout "$2" || usage
 esac