diff --git a/osu.Game/Screens/Edit/Editor.cs b/osu.Game/Screens/Edit/Editor.cs
index 48489c60ab..7955464590 100644
--- a/osu.Game/Screens/Edit/Editor.cs
+++ b/osu.Game/Screens/Edit/Editor.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using JetBrains.Annotations;
 using osu.Framework;
@@ -777,6 +778,8 @@ namespace osu.Game.Screens.Edit
 
             var beatmapSet = beatmapManager.QueryBeatmapSet(bs => bs.ID == Beatmap.Value.BeatmapSetInfo.ID) ?? playableBeatmap.BeatmapInfo.BeatmapSet;
 
+            Debug.Assert(beatmapSet != null);
+
             var difficultyItems = new List<MenuItem>();
 
             foreach (var rulesetBeatmaps in beatmapSet.Beatmaps.GroupBy(b => b.RulesetID).OrderBy(group => group.Key))