diff --git a/osu.Game/Beatmaps/BeatmapManager.cs b/osu.Game/Beatmaps/BeatmapManager.cs
index ff0abd3d78..2e74adbf45 100644
--- a/osu.Game/Beatmaps/BeatmapManager.cs
+++ b/osu.Game/Beatmaps/BeatmapManager.cs
@@ -483,14 +483,20 @@ namespace osu.Game.Beatmaps
             using (var stream = new StreamReader(reader.GetStream(mapName)))
                 metadata = BeatmapDecoder.GetDecoder(stream).Decode(stream).Metadata;
 
-            beatmapSet = new BeatmapSetInfo
+            // check if a set already exists with the same online id.
+            beatmapSet = beatmaps.BeatmapSets.FirstOrDefault(b => b.OnlineBeatmapSetID == metadata.OnlineBeatmapSetID);
+
+            if (beatmapSet == null)
             {
-                OnlineBeatmapSetID = metadata.OnlineBeatmapSetID,
-                Beatmaps = new List<BeatmapInfo>(),
-                Hash = hash,
-                Files = fileInfos,
-                Metadata = metadata
-            };
+                beatmapSet = new BeatmapSetInfo
+                {
+                    OnlineBeatmapSetID = metadata.OnlineBeatmapSetID,
+                    Beatmaps = new List<BeatmapInfo>(),
+                    Hash = hash,
+                    Files = fileInfos,
+                    Metadata = metadata
+                };
+            }
 
             var mapNames = reader.Filenames.Where(f => f.EndsWith(".osu"));
 
@@ -510,16 +516,21 @@ namespace osu.Game.Beatmaps
                     beatmap.BeatmapInfo.Hash = ms.ComputeSHA2Hash();
                     beatmap.BeatmapInfo.MD5Hash = ms.ComputeMD5Hash();
 
-                    // TODO: Diff beatmap metadata with set metadata and leave it here if necessary
-                    beatmap.BeatmapInfo.Metadata = null;
+                    var existing = beatmaps.Beatmaps.FirstOrDefault(b => b.Hash == beatmap.BeatmapInfo.Hash || b.OnlineBeatmapID == beatmap.BeatmapInfo.OnlineBeatmapID);
 
-                    RulesetInfo ruleset = rulesets.GetRuleset(beatmap.BeatmapInfo.RulesetID);
+                    if (existing == null)
+                    {
+                        // TODO: Diff beatmap metadata with set metadata and leave it here if necessary
+                        beatmap.BeatmapInfo.Metadata = null;
 
-                    // TODO: this should be done in a better place once we actually need to dynamically update it.
-                    beatmap.BeatmapInfo.Ruleset = ruleset;
-                    beatmap.BeatmapInfo.StarDifficulty = ruleset?.CreateInstance()?.CreateDifficultyCalculator(beatmap).Calculate() ?? 0;
+                        RulesetInfo ruleset = rulesets.GetRuleset(beatmap.BeatmapInfo.RulesetID);
 
-                    beatmapSet.Beatmaps.Add(beatmap.BeatmapInfo);
+                        // TODO: this should be done in a better place once we actually need to dynamically update it.
+                        beatmap.BeatmapInfo.Ruleset = ruleset;
+                        beatmap.BeatmapInfo.StarDifficulty = ruleset?.CreateInstance()?.CreateDifficultyCalculator(beatmap).Calculate() ?? 0;
+
+                        beatmapSet.Beatmaps.Add(beatmap.BeatmapInfo);
+                    }
                 }
             }