diff --git a/builtin/worktree.c b/builtin/worktree.c
index 4bc7b4f6e7199a..113dbf98d3a145 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -297,17 +297,21 @@ static void remove_junk_on_signal(int signo)
 static const char *worktree_basename(const char *path, int *olen)
 {
 	const char *name;
-	int len;
+	int len, len2;
 
-	len = strlen(path);
+	len2 = len = strlen(path);
 	while (len && is_dir_sep(path[len - 1]))
 		len--;
 
-	for (name = path + len - 1; name > path; name--)
-		if (is_dir_sep(*name)) {
-			name++;
-			break;
-		}
+	if(len) {
+		for (name = path + len - 1; name > path; name--)
+			if (is_dir_sep(*name)) {
+				name++;
+				break;
+			}
+	}
+	else
+		name = path + len2;
 
 	*olen = len;
 	return name;
@@ -492,6 +496,8 @@ static int add_worktree(const char *path, const char *refname,
 		die(_("invalid reference: %s"), refname);
 
 	name = worktree_basename(path, &len);
+	if (!len)
+		die(_("the empty string is not a valid worktree"));
 	strbuf_add(&sb, name, path + len - name);
 	sanitize_refname_component(sb.buf, &sb_name);
 	if (!sb_name.len)