diff --git a/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmap.cs b/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmap.cs
index 69c85fec87..0a248658a8 100644
--- a/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmap.cs
+++ b/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmap.cs
@@ -14,7 +14,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps
         /// <summary>
         /// The definitions for each stage in a <see cref="ManiaPlayfield"/>.
         /// </summary>
-        public readonly List<StageDefinition> Stages;
+        public List<StageDefinition> Stages = new List<StageDefinition>();
 
         /// <summary>
         /// Total number of columns represented by all stages in this <see cref="ManiaBeatmap"/>.
@@ -24,10 +24,10 @@ namespace osu.Game.Rulesets.Mania.Beatmaps
         /// <summary>
         /// Creates a new <see cref="ManiaBeatmap"/>.
         /// </summary>
-        /// <param name="stages">The initial stages.</param>
-        public ManiaBeatmap(List<StageDefinition> stages)
+        /// <param name="defaultStage">The initial stages.</param>
+        public ManiaBeatmap(StageDefinition defaultStage)
         {
-            Stages = stages;
+            Stages.Add(defaultStage);
         }
     }
 }
diff --git a/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs b/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs
index e5a444533d..557ce5eb1b 100644
--- a/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs
+++ b/osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs
@@ -26,7 +26,6 @@ namespace osu.Game.Rulesets.Mania.Beatmaps
         protected override IEnumerable<Type> ValidConversionTypes { get; } = new[] { typeof(IHasXPosition) };
 
         public int TargetColumns;
-        public List<StageDefinition> StageDefinitions;
         public readonly bool IsForCurrentRuleset;
 
         private Pattern lastPattern = new Pattern();
@@ -67,16 +66,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps
             return base.ConvertBeatmap(original);
         }
 
-        protected override Beatmap<ManiaHitObject> CreateBeatmap()
-        {
-            if (StageDefinitions == null)
-                StageDefinitions = new List<StageDefinition>
-                {
-                    new StageDefinition { Columns = TargetColumns }
-                };
-
-            return beatmap = new ManiaBeatmap(StageDefinitions);
-        }
+        protected override Beatmap<ManiaHitObject> CreateBeatmap() => beatmap = new ManiaBeatmap(new StageDefinition { Columns = TargetColumns });
 
         protected override IEnumerable<ManiaHitObject> ConvertHitObject(HitObject original, Beatmap beatmap)
         {
diff --git a/osu.Game.Rulesets.Mania/Mods/ManiaModKeyCoop.cs b/osu.Game.Rulesets.Mania/Mods/ManiaModKeyCoop.cs
index 01fe9863e9..5fbf59e5e6 100644
--- a/osu.Game.Rulesets.Mania/Mods/ManiaModKeyCoop.cs
+++ b/osu.Game.Rulesets.Mania/Mods/ManiaModKeyCoop.cs
@@ -1,15 +1,18 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
+using System;
 using System.Collections.Generic;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Mania.Beatmaps;
 using osu.Game.Rulesets.Mania.Objects;
+using osu.Game.Rulesets.Mania.UI;
 using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.UI;
 
 namespace osu.Game.Rulesets.Mania.Mods
 {
-    public class ManiaModKeyCoop : Mod, IApplicableToBeatmapConverter<ManiaHitObject>
+    public class ManiaModKeyCoop : Mod, IApplicableToBeatmapConverter<ManiaHitObject>, IApplicableToRulesetContainer<ManiaHitObject>
     {
         public override string Name => "KeyCoop";
         public override string ShortenedName => "2P";
@@ -25,16 +28,21 @@ namespace osu.Game.Rulesets.Mania.Mods
             if (mbc.IsForCurrentRuleset)
                 return;
 
-            int originTargetColumns = mbc.TargetColumns;
+            mbc.TargetColumns *= 2;
+        }
 
-            var newStages = new List<StageDefinition>
+        public void ApplyToRulesetContainer(RulesetContainer<ManiaHitObject> rulesetContainer)
+        {
+            var mrc = (ManiaRulesetContainer)rulesetContainer;
+
+            var newDefinitions = new List<StageDefinition>();
+            foreach (var existing in mrc.Beatmap.Stages)
             {
-                new StageDefinition { Columns = originTargetColumns },
-                new StageDefinition { Columns = originTargetColumns },
-            };
+                newDefinitions.Add(new StageDefinition { Columns = (int)Math.Ceiling(existing.Columns / 2f) });
+                newDefinitions.Add(new StageDefinition { Columns = (int)Math.Floor(existing.Columns / 2f) });
+            }
 
-            mbc.StageDefinitions = newStages;
-            mbc.TargetColumns = originTargetColumns * 2;
+            mrc.Beatmap.Stages = newDefinitions;
         }
     }
 }