diff --git a/Scripts/NodeDataCache.cs b/Scripts/NodeDataCache.cs
index 4f4937d..f381845 100644
--- a/Scripts/NodeDataCache.cs
+++ b/Scripts/NodeDataCache.cs
@@ -220,7 +220,6 @@ namespace XNode {
             }
         }
 
-        [System.Serializable]
         private class PortDataCache : Dictionary<System.Type, Dictionary<string, NodePort>> { }
     }
 }