diff --git a/osu.Game.Tests/Visual/SongSelect/TestSceneBeatmapLeaderboard.cs b/osu.Game.Tests/Visual/SongSelect/TestSceneBeatmapLeaderboard.cs
index 07da1790c8..1839821bb5 100644
--- a/osu.Game.Tests/Visual/SongSelect/TestSceneBeatmapLeaderboard.cs
+++ b/osu.Game.Tests/Visual/SongSelect/TestSceneBeatmapLeaderboard.cs
@@ -1,8 +1,6 @@
 // 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;
 using System.Collections.Generic;
 using System.Linq;
@@ -36,10 +34,9 @@ namespace osu.Game.Tests.Visual.SongSelect
         [Cached(typeof(IDialogOverlay))]
         private readonly DialogOverlay dialogOverlay;
 
-        private ScoreManager scoreManager;
-
-        private RulesetStore rulesetStore;
-        private BeatmapManager beatmapManager;
+        private ScoreManager scoreManager = null!;
+        private RulesetStore rulesetStore = null!;
+        private BeatmapManager beatmapManager = null!;
 
         protected override IReadOnlyDependencyContainer CreateChildDependencies(IReadOnlyDependencyContainer parent)
         {
@@ -74,7 +71,7 @@ namespace osu.Game.Tests.Visual.SongSelect
         [Test]
         public void TestLocalScoresDisplay()
         {
-            BeatmapInfo beatmapInfo = null;
+            BeatmapInfo beatmapInfo = null!;
 
             AddStep(@"Set scope", () => leaderboard.Scope = BeatmapLeaderboardScope.Local);
 
@@ -387,7 +384,7 @@ namespace osu.Game.Tests.Visual.SongSelect
         private class FailableLeaderboard : BeatmapLeaderboard
         {
             public new void SetErrorState(LeaderboardState state) => base.SetErrorState(state);
-            public new void SetScores(IEnumerable<ScoreInfo> scores, ScoreInfo userScore = default) => base.SetScores(scores, userScore);
+            public new void SetScores(IEnumerable<ScoreInfo>? scores, ScoreInfo? userScore = null) => base.SetScores(scores, userScore);
         }
     }
 }
diff --git a/osu.Game/Online/Leaderboards/Leaderboard.cs b/osu.Game/Online/Leaderboards/Leaderboard.cs
index 0f444a368a..69b4e5b209 100644
--- a/osu.Game/Online/Leaderboards/Leaderboard.cs
+++ b/osu.Game/Online/Leaderboards/Leaderboard.cs
@@ -1,14 +1,11 @@
 // 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;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Threading;
-using JetBrains.Annotations;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Development;
@@ -54,23 +51,23 @@ namespace osu.Game.Online.Leaderboards
         private readonly Container placeholderContainer;
         private readonly UserTopScoreContainer<TScoreInfo> userScoreContainer;
 
-        private FillFlowContainer<LeaderboardScore> scoreFlowContainer;
+        private FillFlowContainer<LeaderboardScore>? scoreFlowContainer;
 
         private readonly LoadingSpinner loading;
 
-        private CancellationTokenSource currentFetchCancellationSource;
-        private CancellationTokenSource currentScoresAsyncLoadCancellationSource;
+        private CancellationTokenSource? currentFetchCancellationSource;
+        private CancellationTokenSource? currentScoresAsyncLoadCancellationSource;
 
-        private APIRequest fetchScoresRequest;
+        private APIRequest? fetchScoresRequest;
 
         private LeaderboardState state;
 
         [Resolved(CanBeNull = true)]
-        private IAPIProvider api { get; set; }
+        private IAPIProvider? api { get; set; }
 
         private readonly IBindable<APIState> apiState = new Bindable<APIState>();
 
-        private TScope scope;
+        private TScope scope = default!;
 
         public TScope Scope
         {
@@ -179,7 +176,7 @@ namespace osu.Game.Online.Leaderboards
         /// </summary>
         /// <param name="scores">The scores to display.</param>
         /// <param name="userScore">The user top score, if any.</param>
-        protected void SetScores(IEnumerable<TScoreInfo> scores, TScoreInfo userScore = default)
+        protected void SetScores(IEnumerable<TScoreInfo>? scores, TScoreInfo? userScore = default)
         {
             this.scores.Clear();
             if (scores != null)
@@ -213,8 +210,7 @@ namespace osu.Game.Online.Leaderboards
         /// </summary>
         /// <param name="cancellationToken"></param>
         /// <returns>An <see cref="APIRequest"/> responsible for the fetch operation. This will be queued and performed automatically.</returns>
-        [CanBeNull]
-        protected abstract APIRequest FetchScores(CancellationToken cancellationToken);
+        protected abstract APIRequest? FetchScores(CancellationToken cancellationToken);
 
         protected abstract LeaderboardScore CreateDrawableScore(TScoreInfo model, int index);
 
@@ -298,7 +294,7 @@ namespace osu.Game.Online.Leaderboards
 
         #region Placeholder handling
 
-        private Placeholder placeholder;
+        private Placeholder? placeholder;
 
         private void setState(LeaderboardState state)
         {
@@ -325,7 +321,7 @@ namespace osu.Game.Online.Leaderboards
             placeholder.FadeInFromZero(fade_duration, Easing.OutQuint);
         }
 
-        private Placeholder getPlaceholderFor(LeaderboardState state)
+        private Placeholder? getPlaceholderFor(LeaderboardState state)
         {
             switch (state)
             {
diff --git a/osu.Game/Online/Leaderboards/UserTopScoreContainer.cs b/osu.Game/Online/Leaderboards/UserTopScoreContainer.cs
index 2d2d82821c..391e8804f0 100644
--- a/osu.Game/Online/Leaderboards/UserTopScoreContainer.cs
+++ b/osu.Game/Online/Leaderboards/UserTopScoreContainer.cs
@@ -1,8 +1,6 @@
 // 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;
 using System.Threading;
 using osu.Framework.Bindables;
@@ -18,13 +16,15 @@ namespace osu.Game.Online.Leaderboards
     {
         private const int duration = 500;
 
-        public Bindable<TScoreInfo> Score = new Bindable<TScoreInfo>();
+        public Bindable<TScoreInfo?> Score = new Bindable<TScoreInfo?>();
 
         private readonly Container scoreContainer;
         private readonly Func<TScoreInfo, LeaderboardScore> createScoreDelegate;
 
         protected override bool StartHidden => true;
 
+        private CancellationTokenSource? loadScoreCancellation;
+
         public UserTopScoreContainer(Func<TScoreInfo, LeaderboardScore> createScoreDelegate)
         {
             this.createScoreDelegate = createScoreDelegate;
@@ -65,9 +65,7 @@ namespace osu.Game.Online.Leaderboards
             Score.BindValueChanged(onScoreChanged);
         }
 
-        private CancellationTokenSource loadScoreCancellation;
-
-        private void onScoreChanged(ValueChangedEvent<TScoreInfo> score)
+        private void onScoreChanged(ValueChangedEvent<TScoreInfo?> score)
         {
             var newScore = score.NewValue;