@@ -257,6 +257,9 @@ main () {
 		test -e "$arg_prefix" &&
 			die "fatal: prefix '$arg_prefix' already exists."
 		;;
+	split)
+        # checked later against the commit, not the working tree
+        ;;
 	*)
 		test -e "$arg_prefix" ||
 			die "fatal: '$arg_prefix' does not exist; use 'git subtree add'"

@@ -958,13 +961,19 @@ cmd_add_commit () {
 cmd_split () {
 	if test $# -eq 0
 	then
-		rev=$(git rev-parse HEAD)
+			rev=$(git rev-parse HEAD)
 	elif test $# -eq 1 || test $# -eq 2
 	then
-		rev=$(git rev-parse -q --verify "$1^{commit}") ||
-			die "fatal: '$1' does not refer to a commit"
+			rev=$(git rev-parse -q --verify "$1^{commit}") ||
+					die "fatal: '$1' does not refer to a commit"
 	else
-		die "fatal: you must provide exactly one revision, and optionally a repository.  Got: '$*'"
+			die "fatal: you must provide exactly one revision, and optionally a repository.  Got: '$*'"
+	fi
+
+	# Now validate prefix against the commit, not the working tree
+	if ! git ls-tree -d "$rev" -- "$dir" >/dev/null
+	then
+			die "fatal: '$dir' does not exist in commit $rev"
 	fi
 	repository=""
 	if test "$#" = 2