diff --git a/osu.Game/Stores/RealmRulesetStore.cs b/osu.Game/Stores/RealmRulesetStore.cs
index ec395bf774..fb512692d6 100644
--- a/osu.Game/Stores/RealmRulesetStore.cs
+++ b/osu.Game/Stores/RealmRulesetStore.cs
@@ -105,7 +105,11 @@ namespace osu.Game.Stores
             {
                 var rulesets = realm.All<RealmRuleset>();
 
-                List<Ruleset> instances = loadedAssemblies.Values.Select(r => Activator.CreateInstance(r) as Ruleset).OfType<Ruleset>().ToList();
+                List<Ruleset> instances = loadedAssemblies.Values
+                                                          .Select(r => Activator.CreateInstance(r) as Ruleset)
+                                                          .Where(r => r != null)
+                                                          .Cast<Ruleset>()
+                                                          .ToList();
 
                 // add all legacy rulesets first to ensure they have exclusive choice of primary key.
                 foreach (var r in instances.Where(r => r is ILegacyRuleset))