diff --git a/Facepunch.Steamworks/Client/RemoteStorage.File.cs b/Facepunch.Steamworks/Client/RemoteStorage.File.cs
index d554afe..3cac8c8 100644
--- a/Facepunch.Steamworks/Client/RemoteStorage.File.cs
+++ b/Facepunch.Steamworks/Client/RemoteStorage.File.cs
@@ -109,6 +109,8 @@ namespace Facepunch.Steamworks
         /// </summary>
         public RemoteFileWriteStream OpenWrite()
         {
+            if (_isUgc) throw new InvalidOperationException("Cannot write to a shared file.");
+
             return new RemoteFileWriteStream( remoteStorage, this );
         }