diff --git a/src/commands.def b/src/commands.def
index ecc77126af..c352a85c6f 100644
--- a/src/commands.def
+++ b/src/commands.def
@@ -4704,7 +4704,9 @@ struct COMMAND_ARG PUBSUB_SHARDCHANNELS_Args[] = {
 
 #ifndef SKIP_CMD_KEY_SPECS_TABLE
 /* PUBSUB SHARDNUMSUB key specs */
-#define PUBSUB_SHARDNUMSUB_Keyspecs NULL
+keySpec PUBSUB_SHARDNUMSUB_Keyspecs[1] = {
+{NULL,CMD_KEY_NOT_KEY,KSPEC_BS_INDEX,.bs.index={2},KSPEC_FK_RANGE,.fk.range={-1,1,0}}
+};
 #endif
 
 /* PUBSUB SHARDNUMSUB argument table */
@@ -4719,7 +4721,7 @@ struct COMMAND_STRUCT PUBSUB_Subcommands[] = {
 {MAKE_CMD("numpat","Returns a count of unique pattern subscriptions.","O(1)","2.8.0",CMD_DOC_NONE,NULL,NULL,"pubsub",COMMAND_GROUP_PUBSUB,PUBSUB_NUMPAT_History,0,PUBSUB_NUMPAT_Tips,0,pubsubCommand,2,CMD_PUBSUB|CMD_LOADING|CMD_STALE,0,PUBSUB_NUMPAT_Keyspecs,0,NULL,0)},
 {MAKE_CMD("numsub","Returns a count of subscribers to channels.","O(N) for the NUMSUB subcommand, where N is the number of requested channels","2.8.0",CMD_DOC_NONE,NULL,NULL,"pubsub",COMMAND_GROUP_PUBSUB,PUBSUB_NUMSUB_History,0,PUBSUB_NUMSUB_Tips,0,pubsubCommand,-2,CMD_PUBSUB|CMD_LOADING|CMD_STALE,0,PUBSUB_NUMSUB_Keyspecs,0,NULL,1),.args=PUBSUB_NUMSUB_Args},
 {MAKE_CMD("shardchannels","Returns the active shard channels.","O(N) where N is the number of active shard channels, and assuming constant time pattern matching (relatively short shard channels).","7.0.0",CMD_DOC_NONE,NULL,NULL,"pubsub",COMMAND_GROUP_PUBSUB,PUBSUB_SHARDCHANNELS_History,0,PUBSUB_SHARDCHANNELS_Tips,0,pubsubCommand,-2,CMD_PUBSUB|CMD_LOADING|CMD_STALE,0,PUBSUB_SHARDCHANNELS_Keyspecs,0,NULL,1),.args=PUBSUB_SHARDCHANNELS_Args},
-{MAKE_CMD("shardnumsub","Returns the count of subscribers of shard channels.","O(N) for the SHARDNUMSUB subcommand, where N is the number of requested shard channels","7.0.0",CMD_DOC_NONE,NULL,NULL,"pubsub",COMMAND_GROUP_PUBSUB,PUBSUB_SHARDNUMSUB_History,0,PUBSUB_SHARDNUMSUB_Tips,0,pubsubCommand,-2,CMD_PUBSUB|CMD_LOADING|CMD_STALE,0,PUBSUB_SHARDNUMSUB_Keyspecs,0,NULL,1),.args=PUBSUB_SHARDNUMSUB_Args},
+{MAKE_CMD("shardnumsub","Returns the count of subscribers of shard channels.","O(N) for the SHARDNUMSUB subcommand, where N is the number of requested shard channels","7.0.0",CMD_DOC_NONE,NULL,NULL,"pubsub",COMMAND_GROUP_PUBSUB,PUBSUB_SHARDNUMSUB_History,0,PUBSUB_SHARDNUMSUB_Tips,0,pubsubCommand,-2,CMD_PUBSUB|CMD_LOADING|CMD_STALE,0,PUBSUB_SHARDNUMSUB_Keyspecs,1,NULL,1),.args=PUBSUB_SHARDNUMSUB_Args},
 {0}
 };
 
diff --git a/src/commands/pubsub-shardnumsub.json b/src/commands/pubsub-shardnumsub.json
index 8eeca4e31b..1fc3ac13eb 100644
--- a/src/commands/pubsub-shardnumsub.json
+++ b/src/commands/pubsub-shardnumsub.json
@@ -20,6 +20,25 @@
                 "multiple": true
             }
         ],
+        "key_specs": [
+            {
+                "flags": [
+                    "NOT_KEY"
+                ],
+                "begin_search": {
+                    "index": {
+                        "pos": 2
+                    }
+                },
+                "find_keys": {
+                    "range": {
+                        "lastkey": -1,
+                        "step": 1,
+                        "limit": 0
+                    }
+                }
+            }
+        ],
         "reply_schema": {
             "description": "The number of subscribers per shard channel, each even element (including 0th) is channel name, each odd element is the number of subscribers.",
             "type": "array"
diff --git a/tests/unit/cluster/sharded-pubsub.tcl b/tests/unit/cluster/sharded-pubsub.tcl
index b5b19ff481..e3a4f900f5 100644
--- a/tests/unit/cluster/sharded-pubsub.tcl
+++ b/tests/unit/cluster/sharded-pubsub.tcl
@@ -53,4 +53,23 @@ start_cluster 1 1 {tags {external:skip cluster}} {
         catch {[$replica EXEC]} err
         assert_match {EXECABORT*} $err
     }
+
+    test "SHARDNUMSUB for CROSSSLOT Error in cluster mode" {
+        set rd1 [valkey_deferring_client]
+        set rd2 [valkey_deferring_client]
+        set rd3 [valkey_deferring_client]
+
+        assert_equal {1} [ssubscribe $rd1 chan1]
+        assert_equal {1} [ssubscribe $rd2 chan2]
+        assert_error "CROSSSLOT Keys in request don't hash to the same slot" {r pubsub shardnumsub chan1 chan2}
+
+        assert_equal {1} [ssubscribe $rd3 {"{chan1}2"}]
+        assert_equal {chan1 1 {{chan1}2} 1} [r pubsub shardnumsub "chan1" "{chan1}2"]
+
+        # clean up clients
+        $rd1 close
+        $rd2 close
+        $rd3 close
+    }
+
 }
\ No newline at end of file