diff --git a/osu.Game.Tests/Beatmaps/IO/ImportBeatmapTest.cs b/osu.Game.Tests/Beatmaps/IO/ImportBeatmapTest.cs
index f2ab00bead..cd9e765e7f 100644
--- a/osu.Game.Tests/Beatmaps/IO/ImportBeatmapTest.cs
+++ b/osu.Game.Tests/Beatmaps/IO/ImportBeatmapTest.cs
@@ -138,8 +138,9 @@ namespace osu.Game.Tests.Beatmaps.IO
             var set = queryBeatmapSets().First();
 
             foreach (BeatmapInfo b in set.Beatmaps)
+                Assert.IsTrue(set.Beatmaps.Any(c => c.OnlineBeatmapID == b.OnlineBeatmapID));
 
-                Assert.IsTrue(set.Beatmaps.Count > 0);
+            Assert.IsTrue(set.Beatmaps.Count > 0);
 
             var beatmap = store.GetWorkingBeatmap(set.Beatmaps.First(b => b.RulesetID == 0))?.Beatmap;
             Assert.IsTrue(beatmap?.HitObjects.Count > 0);
diff --git a/osu.Game/Beatmaps/BeatmapManager.cs b/osu.Game/Beatmaps/BeatmapManager.cs
index d364a8fbe4..30da9ceae9 100644
--- a/osu.Game/Beatmaps/BeatmapManager.cs
+++ b/osu.Game/Beatmaps/BeatmapManager.cs
@@ -59,8 +59,6 @@ namespace osu.Game.Beatmaps
 
         private readonly FileStore files;
 
-        private readonly OsuDbContext connection;
-
         private readonly RulesetStore rulesets;
 
         private readonly BeatmapStore beatmaps;
@@ -92,7 +90,6 @@ namespace osu.Game.Beatmaps
 
             this.storage = storage;
             this.files = files;
-            this.connection = connection;
             this.rulesets = rulesets;
             this.api = api;
 
@@ -163,7 +160,7 @@ namespace osu.Game.Beatmaps
         /// <param name="archiveReader">The beatmap to be imported.</param>
         public BeatmapSetInfo Import(ArchiveReader archiveReader)
         {
-            BeatmapSetInfo set = null;
+            BeatmapSetInfo set;
 
             // let's only allow one concurrent import at a time for now.
             lock (importLock)
@@ -181,7 +178,8 @@ namespace osu.Game.Beatmaps
             // If we have an ID then we already exist in the database.
             if (beatmapSetInfo.ID != 0) return;
 
-            beatmaps.Add(beatmapSetInfo);
+            lock (beatmaps)
+                beatmaps.Add(beatmapSetInfo);
         }
 
         /// <summary>
@@ -272,13 +270,21 @@ namespace osu.Game.Beatmaps
         /// Delete a beatmap difficulty.
         /// </summary>
         /// <param name="beatmap">The beatmap difficulty to hide.</param>
-        public void Hide(BeatmapInfo beatmap) => beatmaps.Hide(beatmap);
+        public void Hide(BeatmapInfo beatmap)
+        {
+            lock (beatmaps)
+                beatmaps.Hide(beatmap);
+        }
 
         /// <summary>
         /// Restore a beatmap difficulty.
         /// </summary>
         /// <param name="beatmap">The beatmap difficulty to restore.</param>
-        public void Restore(BeatmapInfo beatmap) => beatmaps.Restore(beatmap);
+        public void Restore(BeatmapInfo beatmap)
+        {
+            lock (beatmaps)
+                beatmaps.Restore(beatmap);
+        }
 
         /// <summary>
         /// Returns a <see cref="BeatmapSetInfo"/> to a usable state if it has previously been deleted but not yet purged.
@@ -287,7 +293,8 @@ namespace osu.Game.Beatmaps
         /// <param name="beatmapSet">The beatmap to restore.</param>
         public void Undelete(BeatmapSetInfo beatmapSet)
         {
-            if (!beatmaps.Undelete(beatmapSet)) return;
+            lock (beatmaps)
+                if (!beatmaps.Undelete(beatmapSet)) return;
 
             if (!beatmapSet.Protected)
                 files.Reference(beatmapSet.Files.Select(f => f.FileInfo).ToArray());
@@ -361,7 +368,8 @@ namespace osu.Game.Beatmaps
         /// <returns>Results from the provided query.</returns>
         public List<BeatmapSetInfo> QueryBeatmapSets(Func<BeatmapSetInfo, bool> query)
         {
-            return beatmaps.QueryAndPopulate(query);
+            lock (beatmaps)
+                return beatmaps.QueryAndPopulate(query);
         }
 
         /// <summary>