diff --git a/src/ClientDependency.Core/CompositeFiles/Providers/BaseCompositeFileProcessingProvider.cs b/src/ClientDependency.Core/CompositeFiles/Providers/BaseCompositeFileProcessingProvider.cs
index efd432e..4dbbb7c 100644
--- a/src/ClientDependency.Core/CompositeFiles/Providers/BaseCompositeFileProcessingProvider.cs
+++ b/src/ClientDependency.Core/CompositeFiles/Providers/BaseCompositeFileProcessingProvider.cs
@@ -182,7 +182,8 @@ public CompositeFileDefinition WritePathToStream(ClientDependencyType type, stri
 
             //all config based extensions and all extensions registered by file writers
             var fileBasedExtensions = ClientDependencySettings.Instance.FileBasedDependencyExtensionList
-                                                              .Union(FileWriters.GetRegisteredExtensions());
+                                                              .Union(FileWriters.GetRegisteredExtensions())
+                                                              .ToList();
 
             try
             {