diff --git a/src/cluster.c b/src/cluster.c
index 80cd770188024fbcfc1269bfc18b42efc760b8b0..178ce9b750440655dcf19dff3889c12fbfda9e0d 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -4690,7 +4690,12 @@ void readwriteCommand(redisClient *c) {
  *
  * REDIS_CLUSTER_REDIR_UNSTABLE if the request contains mutliple keys
  * belonging to the same slot, but the slot is not stable (in migration or
- * importing state, likely because a resharding is in progress). */
+ * importing state, likely because a resharding is in progress).
+ *
+ * REDIS_CLUSTER_REDIR_DOWN if the request addresses a slot which is not
+ * bound to any node. In this case the cluster global state should be already
+ * "down" but it is fragile to rely on the update of the global state, so
+ * we also handle it here. */
 clusterNode *getNodeByQuery(redisClient *c, struct redisCommand *cmd, robj **argv, int argc, int *hashslot, int *error_code) {
     clusterNode *n = NULL;
     robj *firstkey = NULL;
@@ -4744,7 +4749,18 @@ clusterNode *getNodeByQuery(redisClient *c, struct redisCommand *cmd, robj **arg
                 firstkey = thiskey;
                 slot = thisslot;
                 n = server.cluster->slots[slot];
-                redisAssertWithInfo(c,firstkey,n != NULL);
+
+                /* Error: If a slot is not served, we are in "cluster down"
+                 * state. However the state is yet to be updated, so this was
+                 * not trapped earlier in processCommand(). Report the same
+                 * error to the client. */
+                if (n == NULL) {
+                    getKeysFreeResult(keyindex);
+                    if (error_code)
+                        *error_code = REDIS_CLUSTER_REDIR_DOWN;
+                    return NULL;
+                }
+
                 /* If we are migrating or importing this slot, we need to check
                  * if we have all the keys in the request (the only way we
                  * can safely serve the request, otherwise we return a TRYAGAIN
diff --git a/src/cluster.h b/src/cluster.h
index ef5caf0d6e6544e9530fef120b9af7a4025aa807..8eaa0ab9816a8e693369cf13abe092733eea3bd3 100644
--- a/src/cluster.h
+++ b/src/cluster.h
@@ -30,6 +30,7 @@
 #define REDIS_CLUSTER_REDIR_UNSTABLE 2      /* Keys in slot resharding. */
 #define REDIS_CLUSTER_REDIR_ASK 3           /* -ASK redirection required. */
 #define REDIS_CLUSTER_REDIR_MOVED 4         /* -MOVED redirection required. */
+#define REDIS_CLUSTER_REDIR_DOWN 5          /* -CLUSTERDOWN error. */
 
 struct clusterNode;
 
diff --git a/src/redis.c b/src/redis.c
index 3ffc62d0293d17b876f3b6d24f9676674d7c529b..918cae1e730e7f747dcc765ba06ead99559a8636 100644
--- a/src/redis.c
+++ b/src/redis.c
@@ -2178,6 +2178,8 @@ int processCommand(redisClient *c) {
                      * but the slot is not "stable" currently as there is
                      * a migration or import in progress. */
                     addReplySds(c,sdsnew("-TRYAGAIN Multiple keys request during rehashing of slot\r\n"));
+                } else if (error_code == REDIS_CLUSTER_REDIR_DOWN) {
+                    addReplySds(c,sdsnew("-CLUSTERDOWN The cluster is down. Hash slot is unbound\r\n"));
                 } else {
                     redisPanic("getNodeByQuery() unknown error.");
                 }