diff --git a/FrostyModSupport/FrostyModExecutor.cs b/FrostyModSupport/FrostyModExecutor.cs
index 70924ca9d..984e670f1 100644
--- a/FrostyModSupport/FrostyModExecutor.cs
+++ b/FrostyModSupport/FrostyModExecutor.cs
@@ -301,9 +301,12 @@ private void ProcessModResources(IResourceContainer fmod)
 
                                 // add in existing bundles
                                 var ebxEntry = am.GetEbxEntry(resource.Name);
-                                foreach (int bid in ebxEntry.Bundles)
+                                if (ebxEntry != null)
                                 {
-                                    bundles.Add(HashBundle(am.GetBundleEntry(bid)));
+                                    foreach (int bid in ebxEntry.Bundles)
+                                    {
+                                        bundles.Add(HashBundle(am.GetBundleEntry(bid)));
+                                    }
                                 }
 
                                 entry.ExtraData = extraData;
diff --git a/FrostyPlugin/Handlers/LegacyCustomActionHandler.cs b/FrostyPlugin/Handlers/LegacyCustomActionHandler.cs
index da4a11ad5..f647258d8 100644
--- a/FrostyPlugin/Handlers/LegacyCustomActionHandler.cs
+++ b/FrostyPlugin/Handlers/LegacyCustomActionHandler.cs
@@ -15,6 +15,8 @@ public sealed class LegacyCustomActionHandler : ILegacyCustomActionHandler
     {
         public HandlerUsage Usage => HandlerUsage.Merge;
 
+        public bool ModifiesAddedAssets => false;
+
         private class ModLegacyFileEntry
         {
             public int Hash { get; set; }
diff --git a/FrostyPlugin/IO/FrostyModWriter.cs b/FrostyPlugin/IO/FrostyModWriter.cs
index d7880ae4e..e2317abb9 100644
--- a/FrostyPlugin/IO/FrostyModWriter.cs
+++ b/FrostyPlugin/IO/FrostyModWriter.cs
@@ -330,7 +330,7 @@ int HashBundle(BundleEntry bentry)
                     if (entry.HasModifiedData)
                     {
                         ICustomActionHandler actionHandler = App.PluginManager.GetCustomHandler(entry.Type);
-                        if (actionHandler != null && !entry.IsAdded)
+                        if (actionHandler != null && (!entry.IsAdded || actionHandler.ModifiesAddedAssets == true))
                         {
                             // use custom action handler to save asset to mod
                             actionHandler.SaveToMod(this, entry);
diff --git a/FrostyPlugin/Mod/IModCustomHandler.cs b/FrostyPlugin/Mod/IModCustomHandler.cs
index fb7947db1..dfbbefe2c 100644
--- a/FrostyPlugin/Mod/IModCustomHandler.cs
+++ b/FrostyPlugin/Mod/IModCustomHandler.cs
@@ -15,6 +15,11 @@ public interface IModCustomActionHandler
         /// </summary>
         HandlerUsage Usage { get; }
 
+        /// <summary>
+        /// Allows custom handlers to be used on duplicated assets which will make them mergable in FMM.
+        /// </summary>
+        bool ModifiesAddedAssets { get; }
+
         /// <summary>
         /// Handles the loading and merging of the custom data.
         /// </summary>
diff --git a/Plugins/BiowareLocalizationPlugin/BiowareLocalizationCustomActionHandler.cs b/Plugins/BiowareLocalizationPlugin/BiowareLocalizationCustomActionHandler.cs
index 51765c31f..65de21b8b 100644
--- a/Plugins/BiowareLocalizationPlugin/BiowareLocalizationCustomActionHandler.cs
+++ b/Plugins/BiowareLocalizationPlugin/BiowareLocalizationCustomActionHandler.cs
@@ -18,6 +18,8 @@ public class BiowareLocalizationCustomActionHandler : ICustomActionHandler
 
         public HandlerUsage Usage => HandlerUsage.Merge;
 
+        public bool ModifiesAddedAssets => false;
+
         // A mod is comprised of a series of base resources, embedded, ebx, res, and chunks. Embedded are used internally
         // for the icon and images of a mod. Ebx/Res/Chunks are the core resources used for applying data to the game.
         // When you create a custom handler, you need to provide your own resources for your custom handled data. This
diff --git a/Plugins/DifficultyWeaponTableDataPlugin/Handlers/DifficultyWeaponTableActionHandler.cs b/Plugins/DifficultyWeaponTableDataPlugin/Handlers/DifficultyWeaponTableActionHandler.cs
index 1620a5506..c0c1989ae 100644
--- a/Plugins/DifficultyWeaponTableDataPlugin/Handlers/DifficultyWeaponTableActionHandler.cs
+++ b/Plugins/DifficultyWeaponTableDataPlugin/Handlers/DifficultyWeaponTableActionHandler.cs
@@ -22,6 +22,8 @@ public class DifficultyWeaponTableActionHandler : ICustomActionHandler
         // data from one mod with another, or does it merge the two together.
         public HandlerUsage Usage => HandlerUsage.Merge;
 
+        public bool ModifiesAddedAssets => false;
+
         // A mod is comprised of a series of base resources, embedded, ebx, res, and chunks. Embedded are used internally
         // for the icon and images of a mod. Ebx/Res/Chunks are the core resources used for applying data to the game.
         // When you create a custom handler, you need to provide your own resources for your custom handled data. This
diff --git a/Plugins/FsLocalizationPlugin/FsLocalizationCustomActionHandler.cs b/Plugins/FsLocalizationPlugin/FsLocalizationCustomActionHandler.cs
index 2fa12ba58..d446183d3 100644
--- a/Plugins/FsLocalizationPlugin/FsLocalizationCustomActionHandler.cs
+++ b/Plugins/FsLocalizationPlugin/FsLocalizationCustomActionHandler.cs
@@ -18,6 +18,8 @@ public class FsLocalizationCustomActionHandler : ICustomActionHandler
     {
         public HandlerUsage Usage => HandlerUsage.Merge;
 
+        public bool ModifiesAddedAssets => false;
+
         private class FsLocalizationResource : EditorModResource
         {
             public override ModResourceType Type => ModResourceType.Ebx;
diff --git a/Plugins/MeshSetPlugin/Handlers/ShaderBlockDepotCustomActionHandler.cs b/Plugins/MeshSetPlugin/Handlers/ShaderBlockDepotCustomActionHandler.cs
index 3d28d4328..84dd2aed7 100644
--- a/Plugins/MeshSetPlugin/Handlers/ShaderBlockDepotCustomActionHandler.cs
+++ b/Plugins/MeshSetPlugin/Handlers/ShaderBlockDepotCustomActionHandler.cs
@@ -13,6 +13,8 @@ public class ShaderBlockDepotCustomActionHandler : ICustomActionHandler
     {
         public HandlerUsage Usage => HandlerUsage.Merge;
 
+        public bool ModifiesAddedAssets => false;
+
         private class ShaderBlockDepotResource : EditorModResource
         {
             public static uint Hash => 0x89ef2205;
diff --git a/Plugins/TestPlugin/Handlers/DifficultyWeaponTableActionHandler.cs b/Plugins/TestPlugin/Handlers/DifficultyWeaponTableActionHandler.cs
index ec2e91e66..d673ca722 100644
--- a/Plugins/TestPlugin/Handlers/DifficultyWeaponTableActionHandler.cs
+++ b/Plugins/TestPlugin/Handlers/DifficultyWeaponTableActionHandler.cs
@@ -18,6 +18,8 @@ public class DifficultyWeaponTableActionHandler : ICustomActionHandler
         // data from one mod with another, or does it merge the two together.
         public HandlerUsage Usage => HandlerUsage.Merge;
 
+        public bool ModifiesAddedAssets => false;
+
         // A mod is comprised of a series of base resources, embedded, ebx, res, and chunks. Embedded are used internally
         // for the icon and images of a mod. Ebx/Res/Chunks are the core resources used for applying data to the game.
         // When you create a custom handler, you need to provide your own resources for your custom handled data. This
diff --git a/Plugins/TestPlugin/Handlers/SvgImageCustomActionHandler.cs b/Plugins/TestPlugin/Handlers/SvgImageCustomActionHandler.cs
index 95c7b4ed4..6b285eab1 100644
--- a/Plugins/TestPlugin/Handlers/SvgImageCustomActionHandler.cs
+++ b/Plugins/TestPlugin/Handlers/SvgImageCustomActionHandler.cs
@@ -18,6 +18,8 @@ public class SvgImageCustomActionHandler : ICustomActionHandler
         // data from one mod with another, or does it merge the two together.
         public HandlerUsage Usage => HandlerUsage.Modify;
 
+        public bool ModifiesAddedAssets => false;
+
         // A mod is comprised of a series of base resources, embedded, ebx, res, and chunks. Embedded are used internally
         // for the icon and images of a mod. Ebx/Res/Chunks are the core resources used for applying data to the game.
         // When you create a custom handler, you need to provide your own resources for your custom handled data. This