diff --git a/lib/SOAP/WSDL/XSD/Typelib/ComplexType.pm b/lib/SOAP/WSDL/XSD/Typelib/ComplexType.pm
index 90888bd..797cb88 100644
--- a/lib/SOAP/WSDL/XSD/Typelib/ComplexType.pm
+++ b/lib/SOAP/WSDL/XSD/Typelib/ComplexType.pm
@@ -155,8 +155,7 @@ sub _factory {
         my $type = $CLASSES_OF{ $class }->{ $name }
             or croak "No class given for $name";
 
-        # require all types here
-        $type->isa('UNIVERSAL')
+        $type->can('serialize')
             or eval "require $type"
                 or croak $@;