diff --git a/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs b/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs
index f4a913b..b48a850 100644
--- a/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs
+++ b/Upsilon/BoundTypes/UserDataBoundTypeDefinition.cs
@@ -217,7 +217,7 @@ namespace Upsilon.BoundTypes
                         var parent =
                             (UserDataBoundTypeDefinition) ((UserDataVariableSymbol) variable).BoundTypeDefinition;
                         if (functionParameter.ActualType != null &&
-                            !string.Equals(functionParameter.ActualType, parent.Name, StringComparison.InvariantCultureIgnoreCase))
+                            !parent.ValidInternalTypes.Any(x => string.Equals(x.Name, functionParameter.ActualType)))
                         {
                             return false;
                         }