diff --git a/osu.Game.Tests/Database/BeatmapImporterTests.cs b/osu.Game.Tests/Database/BeatmapImporterTests.cs
index e2a0e5a79f..4cdcf507b6 100644
--- a/osu.Game.Tests/Database/BeatmapImporterTests.cs
+++ b/osu.Game.Tests/Database/BeatmapImporterTests.cs
@@ -458,7 +458,7 @@ namespace osu.Game.Tests.Database
                 realmFactory.Context.Write(() =>
                 {
                     foreach (var b in imported.Beatmaps)
-                        b.OnlineID = null;
+                        b.OnlineID = -1;
                 });
 
                 deleteBeatmapSet(imported, realmFactory.Context);
@@ -509,8 +509,8 @@ namespace osu.Game.Tests.Database
                 Assert.NotNull(imported);
                 Debug.Assert(imported != null);
 
-                Assert.AreEqual(null, imported.PerformRead(s => s.Beatmaps[0].OnlineID));
-                Assert.AreEqual(null, imported.PerformRead(s => s.Beatmaps[1].OnlineID));
+                Assert.AreEqual(-1, imported.PerformRead(s => s.Beatmaps[0].OnlineID));
+                Assert.AreEqual(-1, imported.PerformRead(s => s.Beatmaps[1].OnlineID));
             });
         }
 
diff --git a/osu.Game/Beatmaps/BeatmapManager.cs b/osu.Game/Beatmaps/BeatmapManager.cs
index 562cbfabf0..0509a9db47 100644
--- a/osu.Game/Beatmaps/BeatmapManager.cs
+++ b/osu.Game/Beatmaps/BeatmapManager.cs
@@ -29,7 +29,7 @@ namespace osu.Game.Beatmaps
     /// Handles general operations related to global beatmap management.
     /// </summary>
     [ExcludeFromDynamicCompile]
-    public class BeatmapManager : IModelDownloader<BeatmapSetInfo>, IModelManager<BeatmapSetInfo>, IModelFileManager<BeatmapSetInfo, BeatmapSetFileInfo>, ICanAcceptFiles, IWorkingBeatmapCache, IDisposable
+    public class BeatmapManager : IModelDownloader<BeatmapSetInfo>, IModelManager<BeatmapSetInfo>, IModelFileManager<BeatmapSetInfo, BeatmapSetFileInfo>, IWorkingBeatmapCache, IDisposable
     {
         private readonly BeatmapModelManager beatmapModelManager;
         private readonly BeatmapModelDownloader beatmapModelDownloader;
diff --git a/osu.Game/Scoring/ScoreManager.cs b/osu.Game/Scoring/ScoreManager.cs
index 8494cdcd22..a9791fba7e 100644
--- a/osu.Game/Scoring/ScoreManager.cs
+++ b/osu.Game/Scoring/ScoreManager.cs
@@ -25,7 +25,7 @@ using osu.Game.Rulesets.Scoring;
 
 namespace osu.Game.Scoring
 {
-    public class ScoreManager : IModelManager<ScoreInfo>, IModelFileManager<ScoreInfo, ScoreFileInfo>, IModelDownloader<ScoreInfo>, ICanAcceptFiles
+    public class ScoreManager : IModelManager<ScoreInfo>, IModelFileManager<ScoreInfo, ScoreFileInfo>, IModelDownloader<ScoreInfo>
     {
         private readonly Scheduler scheduler;
         private readonly Func<BeatmapDifficultyCache> difficulties;
diff --git a/osu.Game/Stores/BeatmapImporter.cs b/osu.Game/Stores/BeatmapImporter.cs
index 5f058872d3..4ff09e6cc5 100644
--- a/osu.Game/Stores/BeatmapImporter.cs
+++ b/osu.Game/Stores/BeatmapImporter.cs
@@ -41,7 +41,7 @@ namespace osu.Game.Stores
         protected override string[] HashableFileTypes => new[] { ".osu" };
 
         // protected override bool CheckLocalAvailability(RealmBeatmapSet model, System.Linq.IQueryable<RealmBeatmapSet> items)
-        //     => base.CheckLocalAvailability(model, items) || (model.OnlineID != null && items.Any(b => b.OnlineID == model.OnlineID));
+        //     => base.CheckLocalAvailability(model, items) || (model.OnlineID > -1));
 
         private readonly BeatmapOnlineLookupQueue? onlineLookupQueue;
 
@@ -74,9 +74,9 @@ namespace osu.Game.Stores
             // ensure at least one beatmap was able to retrieve or keep an online ID, else drop the set ID.
             if (hadOnlineBeatmapIDs && !beatmapSet.Beatmaps.Any(b => b.OnlineID > 0))
             {
-                if (beatmapSet.OnlineID != null)
+                if (beatmapSet.OnlineID > -1)
                 {
-                    beatmapSet.OnlineID = null;
+                    beatmapSet.OnlineID = -1;
                     LogForModel(beatmapSet, "Disassociating beatmap set ID due to loss of all beatmap IDs");
                 }
             }
@@ -91,17 +91,17 @@ namespace osu.Game.Stores
             // If this is ever an issue, we can consider marking as pending delete but not resetting the IDs (but care will be required for
             // beatmaps, which don't have their own `DeletePending` state).
 
-            if (beatmapSet.OnlineID != null)
+            if (beatmapSet.OnlineID > -1)
             {
                 var existingOnlineId = realm.All<RealmBeatmapSet>().SingleOrDefault(b => b.OnlineID == beatmapSet.OnlineID);
 
                 if (existingOnlineId != null)
                 {
                     existingOnlineId.DeletePending = true;
-                    existingOnlineId.OnlineID = null;
+                    existingOnlineId.OnlineID = -1;
 
                     foreach (var b in existingOnlineId.Beatmaps)
-                        b.OnlineID = null;
+                        b.OnlineID = -1;
 
                     LogForModel(beatmapSet, $"Found existing beatmap set with same OnlineID ({beatmapSet.OnlineID}). It will be deleted.");
                 }
@@ -110,7 +110,7 @@ namespace osu.Game.Stores
 
         private void validateOnlineIds(RealmBeatmapSet beatmapSet, Realm realm)
         {
-            var beatmapIds = beatmapSet.Beatmaps.Where(b => b.OnlineID.HasValue).Select(b => b.OnlineID).ToList();
+            var beatmapIds = beatmapSet.Beatmaps.Where(b => b.OnlineID > -1).Select(b => b.OnlineID).ToList();
 
             // ensure all IDs are unique
             if (beatmapIds.GroupBy(b => b).Any(g => g.Count() > 1))
@@ -140,7 +140,7 @@ namespace osu.Game.Stores
                 }
             }
 
-            void resetIds() => beatmapSet.Beatmaps.ForEach(b => b.OnlineID = null);
+            void resetIds() => beatmapSet.Beatmaps.ForEach(b => b.OnlineID = -1);
         }
 
         protected override bool CanSkipImport(RealmBeatmapSet existing, RealmBeatmapSet import)
@@ -148,7 +148,7 @@ namespace osu.Game.Stores
             if (!base.CanSkipImport(existing, import))
                 return false;
 
-            return existing.Beatmaps.Any(b => b.OnlineID != null);
+            return existing.Beatmaps.Any(b => b.OnlineID > -1);
         }
 
         protected override bool CanReuseExisting(RealmBeatmapSet existing, RealmBeatmapSet import)
@@ -182,7 +182,7 @@ namespace osu.Game.Stores
 
             return new RealmBeatmapSet
             {
-                OnlineID = beatmap.BeatmapInfo.BeatmapSet?.OnlineBeatmapSetID,
+                OnlineID = beatmap.BeatmapInfo.BeatmapSet?.OnlineBeatmapSetID ?? -1,
                 // Metadata = beatmap.Metadata,
                 DateAdded = DateTimeOffset.UtcNow
             };
@@ -250,7 +250,7 @@ namespace osu.Game.Stores
                     {
                         Hash = hash,
                         DifficultyName = decodedInfo.Version,
-                        OnlineID = decodedInfo.OnlineBeatmapID,
+                        OnlineID = decodedInfo.OnlineBeatmapID ?? -1,
                         AudioLeadIn = decodedInfo.AudioLeadIn,
                         StackLeniency = decodedInfo.StackLeniency,
                         SpecialStyle = decodedInfo.SpecialStyle,