diff --git a/osu.Game/Beatmaps/BeatmapSetInfo.cs b/osu.Game/Beatmaps/BeatmapSetInfo.cs
index 35468ce831..1806c2b491 100644
--- a/osu.Game/Beatmaps/BeatmapSetInfo.cs
+++ b/osu.Game/Beatmaps/BeatmapSetInfo.cs
@@ -5,7 +5,6 @@
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
-using JetBrains.Annotations;
 using osu.Framework.Testing;
 using osu.Game.Database;
 using osu.Game.Extensions;
@@ -34,8 +33,7 @@ public int? OnlineID
 
         public BeatmapSetOnlineStatus Status { get; set; } = BeatmapSetOnlineStatus.None;
 
-        [NotNull]
-        public List<BeatmapSetFileInfo> Files { get; set; } = new List<BeatmapSetFileInfo>();
+        public List<BeatmapSetFileInfo> Files { get; } = new List<BeatmapSetFileInfo>();
 
         /// <summary>
         /// The maximum star difficulty of all beatmaps in this set.
diff --git a/osu.Game/Database/ArchiveModelManager.cs b/osu.Game/Database/ArchiveModelManager.cs
index a0e8105285..adbb71c8da 100644
--- a/osu.Game/Database/ArchiveModelManager.cs
+++ b/osu.Game/Database/ArchiveModelManager.cs
@@ -392,7 +392,8 @@ void rollback()
             {
                 LogForModel(item, @"Beginning import...");
 
-                item.Files = archive != null ? createFileInfos(archive, Files) : new List<TFileModel>();
+                if (archive != null)
+                    item.Files.AddRange(createFileInfos(archive, Files));
                 item.Hash = ComputeHash(item);
 
                 await Populate(item, archive, cancellationToken).ConfigureAwait(false);
diff --git a/osu.Game/Database/IHasFiles.cs b/osu.Game/Database/IHasFiles.cs
index f6aa941ec2..3f6531832f 100644
--- a/osu.Game/Database/IHasFiles.cs
+++ b/osu.Game/Database/IHasFiles.cs
@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
+using JetBrains.Annotations;
 
 namespace osu.Game.Database
 {
@@ -12,7 +13,8 @@ namespace osu.Game.Database
     public interface IHasFiles<TFile>
         where TFile : INamedFileInfo
     {
-        List<TFile> Files { get; set; }
+        [NotNull]
+        List<TFile> Files { get; }
 
         string Hash { get; set; }
     }
diff --git a/osu.Game/Online/Leaderboards/LeaderboardScore.cs b/osu.Game/Online/Leaderboards/LeaderboardScore.cs
index 26749a23f9..f0c57cb953 100644
--- a/osu.Game/Online/Leaderboards/LeaderboardScore.cs
+++ b/osu.Game/Online/Leaderboards/LeaderboardScore.cs
@@ -394,7 +394,7 @@ public MenuItem[] ContextMenuItems
                 if (Score.Mods.Length > 0 && modsContainer.Any(s => s.IsHovered) && songSelect != null)
                     items.Add(new OsuMenuItem("Use these mods", MenuItemType.Highlighted, () => songSelect.Mods.Value = Score.Mods));
 
-                if (Score.Files?.Count > 0)
+                if (Score.Files.Count > 0)
                     items.Add(new OsuMenuItem("Export", MenuItemType.Standard, () => scoreManager.Export(Score)));
 
                 if (Score.ID != 0)
diff --git a/osu.Game/Scoring/ScoreInfo.cs b/osu.Game/Scoring/ScoreInfo.cs
index 736a939a59..b4e194cbed 100644
--- a/osu.Game/Scoring/ScoreInfo.cs
+++ b/osu.Game/Scoring/ScoreInfo.cs
@@ -160,7 +160,7 @@ public string StatisticsJson
         [NotMapped]
         public List<HitEvent> HitEvents { get; set; }
 
-        public List<ScoreFileInfo> Files { get; set; }
+        public List<ScoreFileInfo> Files { get; } = new List<ScoreFileInfo>();
 
         public string Hash { get; set; }
 
diff --git a/osu.Game/Skinning/Skin.cs b/osu.Game/Skinning/Skin.cs
index fae1a599d1..10526b69af 100644
--- a/osu.Game/Skinning/Skin.cs
+++ b/osu.Game/Skinning/Skin.cs
@@ -59,7 +59,7 @@ protected Skin(SkinInfo skin, IStorageResourceProvider resources, [CanBeNull] St
                 string filename = $"{skinnableTarget}.json";
 
                 // skininfo files may be null for default skin.
-                var fileInfo = SkinInfo.Files?.FirstOrDefault(f => f.Filename == filename);
+                var fileInfo = SkinInfo.Files.FirstOrDefault(f => f.Filename == filename);
 
                 if (fileInfo == null)
                     continue;
diff --git a/osu.Game/Skinning/SkinInfo.cs b/osu.Game/Skinning/SkinInfo.cs
index 3b34e23d57..4733e8cdd9 100644
--- a/osu.Game/Skinning/SkinInfo.cs
+++ b/osu.Game/Skinning/SkinInfo.cs
@@ -36,7 +36,7 @@ public virtual Skin CreateInstance(IStorageResourceProvider resources)
             return (Skin)Activator.CreateInstance(type, this, resources);
         }
 
-        public List<SkinFileInfo> Files { get; set; } = new List<SkinFileInfo>();
+        public List<SkinFileInfo> Files { get; } = new List<SkinFileInfo>();
 
         public bool DeletePending { get; set; }