[DGD] Labeled inheritance riddle

[Maciek]

Hello,

am I doing something wrong or is it a bug?
(/src/Changelog says "Functions and variables need not be unique between 
labeled inherited objects.")

inherit lib_string SYSTEM_LIB + "string";
inherit mu MARKUP;

throws:

/u/System/lib/io.c, 253: inherited multiple instances of:
/u/System/lib/io.c, 253:   center (/u/System/lib/markup, 
/u/System/lib/string)

Thanks.