diff --git a/Upsilon/Binder/VariableSymbols/InternalFunctionVariableSymbol.cs b/Upsilon/Binder/VariableSymbols/InternalFunctionVariableSymbol.cs
index 8f7de5b..e92d467 100644
--- a/Upsilon/Binder/VariableSymbols/InternalFunctionVariableSymbol.cs
+++ b/Upsilon/Binder/VariableSymbols/InternalFunctionVariableSymbol.cs
@@ -41,6 +41,8 @@ namespace Upsilon.Binder.VariableSymbols
                     {
                         continue;
                     }
+                    if (functionParameter.ValidTypes == Type.Unknown)
+                        continue;
 
                     if (!functionParameter.ValidTypes.Type.HasFlag(callingParameter.Type))
                     {