diff --git a/src/sentinel.c b/src/sentinel.c
index 4c561586..be0cf071 100644
--- a/src/sentinel.c
+++ b/src/sentinel.c
@@ -2810,6 +2810,7 @@ void sentinelCommand(redisClient *c) {
         sentinelRedisInstance *ri;
         int usable;
 
+        if (c->argc != 3) goto numargserr;
         if ((ri = sentinelGetMasterByNameOrReplyError(c,c->argv[2]))
             == NULL) return;
         int result = sentinelIsQuorumReachable(ri,&usable);