diff --git a/big_tests/tests/graphql_muc_SUITE.erl b/big_tests/tests/graphql_muc_SUITE.erl
index 69c7651434a..4c722127fc7 100644
--- a/big_tests/tests/graphql_muc_SUITE.erl
+++ b/big_tests/tests/graphql_muc_SUITE.erl
@@ -989,7 +989,7 @@ user_try_create_instant_room_with_invalid_name(Config) ->
 
 user_try_create_instant_room_with_invalid_name_story(Config, Alice) ->
     Res = user_create_instant_room(Alice, muc_helper:muc_host(), <<"test room">>, <<"Ali">>, Config),
-    ?assertNotEqual(nomatch, binary:match(get_err_msg(Res), <<"Room name or domain are invalid">>)).
+    ?assertNotEqual(nomatch, binary:match(get_err_msg(Res), <<"Room name or domain is invalid">>)).
 
 user_try_delete_nonexistent_room(Config) ->
     escalus:fresh_story_with_config(Config, [{alice, 1}],
diff --git a/src/mod_muc_api.erl b/src/mod_muc_api.erl
index 84ab12d3118..5290d8bd178 100644
--- a/src/mod_muc_api.erl
+++ b/src/mod_muc_api.erl
@@ -115,7 +115,7 @@ create_instant_room(MUCDomain, Name, OwnerJID, Nick) ->
                     Error
             end;
         {true, error} ->
-            {invalid_input, "Room name or domain are invalid"};
+            {invalid_input, "Room name or domain is invalid"};
         {false, _} ->
             ?USER_NOT_FOUND_RESULT
     end.