diff --git a/osu.Game/Online/Solo/SoloStatisticsWatcher.cs b/osu.Game/Online/Solo/SoloStatisticsWatcher.cs
index 383f6a202d..33344044b9 100644
--- a/osu.Game/Online/Solo/SoloStatisticsWatcher.cs
+++ b/osu.Game/Online/Solo/SoloStatisticsWatcher.cs
@@ -62,7 +62,7 @@ namespace osu.Game.Online.Solo
                 return;
             }
 
-            callbacks[score.OnlineID] = callback;
+            callbacks.Add(score.OnlineID, callback);
         });
 
         private void onUserChanged(APIUser? localUser) => Schedule(() =>