diff --git a/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs b/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs
index b48a850..fcc4fd1 100644
--- a/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs
+++ b/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs
@@ -23,7 +23,7 @@ namespace Upsilon.BoundTypes
         }
 
         public UserDataBoundTypeDefinition(string name, Dictionary<string, UserDataBoundProperty> backingType)
-            : base(new TypeContainer(name), typeof(void))
+            : base(new TypeContainer(name), new System.Type[0])
         {
             Name = name;
             Properties = backingType;
@@ -216,10 +216,17 @@ namespace Upsilon.BoundTypes
                     {
                         var parent =
                             (UserDataBoundTypeDefinition) ((UserDataVariableSymbol) variable).BoundTypeDefinition;
-                        if (functionParameter.ActualType != null &&
-                            !parent.ValidInternalTypes.Any(x => string.Equals(x.Name, functionParameter.ActualType)))
+                        if (parent.ValidInternalTypes.Length != 0)
                         {
-                            return false;
+                            if (functionParameter.ActualType != null &&
+                                !parent.ValidInternalTypes.Any(x => string.Equals(x.Name, functionParameter.ActualType)))
+                            {
+                                return false;
+                            }
+                            if (!string.Equals(parent.Name, functionParameter.ActualType, StringComparison.InvariantCultureIgnoreCase))
+                            {
+                                return false;
+                            }
                         }
                     }
                 }