diff --git a/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs b/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs
index fcba2d259..c40403ba9 100644
--- a/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs
+++ b/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs
@@ -188,9 +188,18 @@ public Task<WritingSystem> CreateWritingSystem(WritingSystemType type, WritingSy
         return Task.FromResult(FromLcmWritingSystem(ws, index, type));
     }
 
-    public Task<WritingSystem> UpdateWritingSystem(WritingSystemId id, WritingSystemType type, UpdateObjectInput<WritingSystem> update)
+    public async Task<WritingSystem> UpdateWritingSystem(WritingSystemId id, WritingSystemType type, UpdateObjectInput<WritingSystem> update)
     {
-        throw new NotImplementedException(); // TODO: This needs to be implemented now, because UpdateWritingSystem(before, after) needs to call this
+        Cache.ServiceLocator.WritingSystemManager.GetOrSet(id.Code, out var lcmWritingSystem);
+        await Cache.DoUsingNewOrCurrentUOW("Update WritingSystem",
+            "Revert WritingSystem",
+            async () =>
+            {
+                var updateProxy = new UpdateWritingSystemProxy(lcmWritingSystem, this) { Type = type }; // TODO: Doesn't compile, wants Font to be set. Also wants a GUID Id which we don't have...
+                update.Apply(updateProxy);
+                updateProxy.CommitUpdate(Cache);
+            });
+        return await GetWritingSystem(id, type);
     }
 
     public async Task<WritingSystem> UpdateWritingSystem(WritingSystem before, WritingSystem after)
diff --git a/backend/FwLite/FwDataMiniLcmBridge/Api/UpdateProxy/UpdateWritingSystemProxy.cs b/backend/FwLite/FwDataMiniLcmBridge/Api/UpdateProxy/UpdateWritingSystemProxy.cs
new file mode 100644
index 000000000..ee67bcf43
--- /dev/null
+++ b/backend/FwLite/FwDataMiniLcmBridge/Api/UpdateProxy/UpdateWritingSystemProxy.cs
@@ -0,0 +1,58 @@
+using MiniLcm.Models;
+using SIL.LCModel;
+using SIL.LCModel.Core.WritingSystems;
+using SIL.LCModel.DomainServices;
+
+namespace FwDataMiniLcmBridge.Api.UpdateProxy;
+
+public record UpdateWritingSystemProxy : WritingSystem
+{
+    private readonly CoreWritingSystemDefinition _origLcmWritingSystem;
+    private readonly CoreWritingSystemDefinition _workingLcmWritingSystem;
+    private readonly FwDataMiniLcmApi _lexboxLcmApi;
+
+    public UpdateWritingSystemProxy(CoreWritingSystemDefinition lcmWritingSystem, FwDataMiniLcmApi lexboxLcmApi)
+    {
+        _origLcmWritingSystem = lcmWritingSystem;
+        _workingLcmWritingSystem = new CoreWritingSystemDefinition(lcmWritingSystem, cloneId: true);
+        _lexboxLcmApi = lexboxLcmApi;
+    }
+
+    public void CommitUpdate(LcmCache cache)
+    {
+        if (_workingLcmWritingSystem.Id == _origLcmWritingSystem.Id)
+        {
+            cache.ServiceLocator.WritingSystemManager.Set(_workingLcmWritingSystem);
+        }
+        else
+        {
+            // Changing the ID of a writing system requires LCM to do a lot of work, so only go through that process if absolutely required
+            WritingSystemServices.MergeWritingSystems(cache, _workingLcmWritingSystem, _origLcmWritingSystem);
+        }
+    }
+
+    public override required WritingSystemId WsId
+    {
+        get => _workingLcmWritingSystem.Id;
+        set => _workingLcmWritingSystem.Id = value;
+    }
+
+    public override required string Name
+    {
+        get => _workingLcmWritingSystem.LanguageName;
+        set { } // Silently do nothing; name should be derived from WsId at all times, so if the name should change then so should the WsId
+    }
+
+    public override required string Abbreviation
+    {
+        get => _workingLcmWritingSystem.Abbreviation;
+        set => _workingLcmWritingSystem.Abbreviation = value;
+    }
+
+    // TODO: Change WritingSystem Font property to be a list of strings instead of a single string, then do something like this
+    // public override required List<string> Fonts
+    // {
+    //     get => _workingLcmWritingSystem.Fonts.Select(f => f.Name).ToList();
+    //     set => throw new NotImplementedException();
+    // }
+}
diff --git a/backend/FwLite/MiniLcm/Models/WritingSystem.cs b/backend/FwLite/MiniLcm/Models/WritingSystem.cs
index ed96bcddc..253f2dc28 100644
--- a/backend/FwLite/MiniLcm/Models/WritingSystem.cs
+++ b/backend/FwLite/MiniLcm/Models/WritingSystem.cs
@@ -3,10 +3,11 @@
 public record WritingSystem: IObjectWithId
 {
     public required Guid Id { get; set; }
-    public required WritingSystemId WsId { get; set; }
-    public required string Name { get; set; }
-    public required string Abbreviation { get; set; }
-    public required string Font { get; set; }
+    public virtual required WritingSystemId WsId { get; set; }
+    public virtual required string Name { get; set; }
+    public virtual required string Abbreviation { get; set; }
+    // TODO: Font will need to become Fonts, a list or array of strings, to better match the LCM model
+    public virtual required string Font { get; set; }
 
     public DateTimeOffset? DeletedAt { get; set; }
     public required WritingSystemType Type { get; set; }