diff --git a/osu.Game.Rulesets.Karaoke/KaraokeRuleset.cs b/osu.Game.Rulesets.Karaoke/KaraokeRuleset.cs
index cc8f2739a..bb5e0d0aa 100644
--- a/osu.Game.Rulesets.Karaoke/KaraokeRuleset.cs
+++ b/osu.Game.Rulesets.Karaoke/KaraokeRuleset.cs
@@ -198,7 +198,7 @@ public override IResourceStore<byte[]> CreateResourceStore()
 
         public override string PlayingVerb => "Singing karaoke";
 
-        public override ISkin? CreateSkinTransformer(ISkin skin, IBeatmap beatmap)
+        public override ISkin CreateSkinTransformer(ISkin skin, IBeatmap beatmap)
         {
             return skin switch
             {
@@ -206,7 +206,7 @@ public override IResourceStore<byte[]> CreateResourceStore()
                 ArgonSkin => new KaraokeArgonSkinTransformer(skin, beatmap),
                 DefaultLegacySkin => new KaraokeClassicSkinTransformer(skin, beatmap),
                 LegacySkin => new KaraokeLegacySkinTransformer(skin, beatmap),
-                _ => null
+                _ => throw new InvalidOperationException(),
             };
         }