diff --git a/osu.Game.Tests/Editing/Checks/CheckAudioQualityTest.cs b/osu.Game.Tests/Editing/Checks/CheckAudioQualityTest.cs
index 3a2cdaf233..8e269cbab2 100644
--- a/osu.Game.Tests/Editing/Checks/CheckAudioQualityTest.cs
+++ b/osu.Game.Tests/Editing/Checks/CheckAudioQualityTest.cs
@@ -5,6 +5,7 @@ using System.Linq;
 using Moq;
 using NUnit.Framework;
 using osu.Framework.Audio.Track;
+using osu.Framework.Extensions.ObjectExtensions;
 using osu.Framework.Timing;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Edit;
@@ -41,7 +42,7 @@ namespace osu.Game.Tests.Editing.Checks
 
             var mock = new Mock<IWorkingBeatmap>();
             mock.SetupGet(w => w.Beatmap).Returns(beatmap);
-            mock.SetupGet(w => w.Track).Returns((Track)null);
+            mock.SetupGet(w => w.Track).Returns(default(Track?).AsNonNull());
 
             Assert.That(check.Run(new BeatmapVerifierContext(beatmap, mock.Object)), Is.Empty);
         }
diff --git a/osu.Game.Tests/Editing/Checks/CheckBackgroundQualityTest.cs b/osu.Game.Tests/Editing/Checks/CheckBackgroundQualityTest.cs
index 5d3fd9cd65..1aead6d78c 100644
--- a/osu.Game.Tests/Editing/Checks/CheckBackgroundQualityTest.cs
+++ b/osu.Game.Tests/Editing/Checks/CheckBackgroundQualityTest.cs
@@ -6,6 +6,7 @@ using System.IO;
 using System.Linq;
 using Moq;
 using NUnit.Framework;
+using osu.Framework.Extensions.ObjectExtensions;
 using osu.Framework.Graphics.Rendering.Dummy;
 using osu.Framework.Graphics.Textures;
 using osu.Game.Beatmaps;
@@ -131,7 +132,7 @@ namespace osu.Game.Tests.Editing.Checks
 
             var mock = new Mock<IWorkingBeatmap>();
             mock.SetupGet(w => w.Beatmap).Returns(beatmap);
-            mock.SetupGet(w => w.Background).Returns(background);
+            mock.SetupGet(w => w.Background).Returns(background.AsNonNull());
             mock.Setup(w => w.GetStream(It.IsAny<string>())).Returns(stream);
 
             return mock;
diff --git a/osu.Game.Tests/Editing/Checks/CheckZeroByteFilesTest.cs b/osu.Game.Tests/Editing/Checks/CheckZeroByteFilesTest.cs
index 5c66e1beaa..7c2b1690af 100644
--- a/osu.Game.Tests/Editing/Checks/CheckZeroByteFilesTest.cs
+++ b/osu.Game.Tests/Editing/Checks/CheckZeroByteFilesTest.cs
@@ -5,6 +5,7 @@ using System.IO;
 using System.Linq;
 using Moq;
 using NUnit.Framework;
+using osu.Framework.Extensions.ObjectExtensions;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Edit;
 using osu.Game.Rulesets.Edit.Checks;
@@ -72,7 +73,7 @@ namespace osu.Game.Tests.Editing.Checks
         private BeatmapVerifierContext getContextMissing()
         {
             var mockWorkingBeatmap = new Mock<IWorkingBeatmap>();
-            mockWorkingBeatmap.Setup(w => w.GetStream(It.IsAny<string>())).Returns((Stream)null);
+            mockWorkingBeatmap.Setup(w => w.GetStream(It.IsAny<string>())).Returns(default(Stream?).AsNonNull());
 
             return new BeatmapVerifierContext(beatmap, mockWorkingBeatmap.Object);
         }