diff --git a/builtin-show-ref.c b/builtin-show-ref.c
index 853f13f6ae9df60e340a6988a9d74bb246df4df6..75211e64f9a850be95de3b85edaafdf0d9a5886a 100644
--- a/builtin-show-ref.c
+++ b/builtin-show-ref.c
@@ -221,9 +221,11 @@ int cmd_show_ref(int argc, const char **argv, const char *prefix)
 	}
 
 	if (verify) {
-		unsigned char sha1[20];
-
+		if (!pattern)
+			die("--verify requires a reference");
 		while (*pattern) {
+			unsigned char sha1[20];
+
 			if (!strncmp(*pattern, "refs/", 5) &&
 			    resolve_ref(*pattern, sha1, 1, NULL)) {
 				if (!quiet)