diff --git a/osu.Game.Rulesets.Taiko/Mods/TaikoModClassic.cs b/osu.Game.Rulesets.Taiko/Mods/TaikoModClassic.cs
index 704185cc3c..9f82d54e65 100644
--- a/osu.Game.Rulesets.Taiko/Mods/TaikoModClassic.cs
+++ b/osu.Game.Rulesets.Taiko/Mods/TaikoModClassic.cs
@@ -1,10 +1,9 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System.Linq;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Judgements;
@@ -21,7 +20,7 @@ namespace osu.Game.Rulesets.Taiko.Mods
 {
     public class TaikoModClassic : ModClassic, IApplicableToDrawableRuleset<TaikoHitObject>, IUpdatableByPlayfield, IApplicableAfterBeatmapConversion
     {
-        private DrawableTaikoRuleset drawableTaikoRuleset;
+        private DrawableTaikoRuleset? drawableTaikoRuleset;
 
         public void ApplyToDrawableRuleset(DrawableRuleset<TaikoHitObject> drawableRuleset)
         {
@@ -160,6 +159,8 @@ namespace osu.Game.Rulesets.Taiko.Mods
             // Classic taiko scrolls at a constant 100px per 1000ms. More notes become visible as the playfield is lengthened.
             const float scroll_rate = 10;
 
+            Debug.Assert(drawableTaikoRuleset != null);
+
             // Since the time range will depend on a positional value, it is referenced to the x480 pixel space.
             float ratio = drawableTaikoRuleset.DrawHeight / 480;