diff --git a/osu.Game.Tests/Beatmaps/BeatmapDifficultyManagerTest.cs b/osu.Game.Tests/Beatmaps/BeatmapDifficultyManagerTest.cs
new file mode 100644
index 0000000000..0f6d956b3c
--- /dev/null
+++ b/osu.Game.Tests/Beatmaps/BeatmapDifficultyManagerTest.cs
@@ -0,0 +1,32 @@
+// 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.
+
+using NUnit.Framework;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Osu.Mods;
+
+namespace osu.Game.Tests.Beatmaps
+{
+    [TestFixture]
+    public class BeatmapDifficultyManagerTest
+    {
+        [Test]
+        public void TestKeyEqualsWithDifferentModInstances()
+        {
+            var key1 = new BeatmapDifficultyManager.DifficultyCacheLookup(1234, 0, new Mod[] { new OsuModHardRock(), new OsuModHidden() });
+            var key2 = new BeatmapDifficultyManager.DifficultyCacheLookup(1234, 0, new Mod[] { new OsuModHardRock(), new OsuModHidden() });
+
+            Assert.That(key1, Is.EqualTo(key2));
+        }
+
+        [Test]
+        public void TestKeyEqualsWithDifferentModOrder()
+        {
+            var key1 = new BeatmapDifficultyManager.DifficultyCacheLookup(1234, 0, new Mod[] { new OsuModHardRock(), new OsuModHidden() });
+            var key2 = new BeatmapDifficultyManager.DifficultyCacheLookup(1234, 0, new Mod[] { new OsuModHidden(), new OsuModHardRock() });
+
+            Assert.That(key1, Is.EqualTo(key2));
+        }
+    }
+}
diff --git a/osu.Game/Beatmaps/BeatmapDifficultyManager.cs b/osu.Game/Beatmaps/BeatmapDifficultyManager.cs
index b80b4e45ed..0100c9b210 100644
--- a/osu.Game/Beatmaps/BeatmapDifficultyManager.cs
+++ b/osu.Game/Beatmaps/BeatmapDifficultyManager.cs
@@ -89,8 +89,14 @@ namespace osu.Game.Beatmaps
             if (tryGetExisting(beatmapInfo, rulesetInfo, mods, out var existing, out var key))
                 return existing;
 
-            return await Task.Factory.StartNew(() => computeDifficulty(key, beatmapInfo, rulesetInfo), cancellationToken,
-                TaskCreationOptions.HideScheduler | TaskCreationOptions.RunContinuationsAsynchronously, updateScheduler);
+            return await Task.Factory.StartNew(() =>
+            {
+                // Computation may have finished in a previous task.
+                if (tryGetExisting(beatmapInfo, rulesetInfo, mods, out existing, out _))
+                    return existing;
+
+                return computeDifficulty(key, beatmapInfo, rulesetInfo);
+            }, cancellationToken, TaskCreationOptions.HideScheduler | TaskCreationOptions.RunContinuationsAsynchronously, updateScheduler);
         }
 
         /// <summary>
@@ -245,7 +251,7 @@ namespace osu.Game.Beatmaps
             updateScheduler?.Dispose();
         }
 
-        private readonly struct DifficultyCacheLookup : IEquatable<DifficultyCacheLookup>
+        public readonly struct DifficultyCacheLookup : IEquatable<DifficultyCacheLookup>
         {
             public readonly int BeatmapId;
             public readonly int RulesetId;
@@ -261,7 +267,7 @@ namespace osu.Game.Beatmaps
             public bool Equals(DifficultyCacheLookup other)
                 => BeatmapId == other.BeatmapId
                    && RulesetId == other.RulesetId
-                   && Mods.SequenceEqual(other.Mods);
+                   && Mods.Select(m => m.Acronym).SequenceEqual(other.Mods.Select(m => m.Acronym));
 
             public override int GetHashCode()
             {