TStringList amibiguity between classes when using dupIgnore

Hello

I have created TStringList *ST. And When I need to use ST->Duplicates=dupIgnore, I get ambiguity between classes: "System:Classes" and "System::Types". Looks like compiler does not know which classes to use. TStringList belongs to class System::Classes. How can I tell to compiler that use class System::classes where TStringList belongs?

thanks

Jarkko Halme