Doxygen - any way to get a module hierarchy?

It seems that even if I specify my groups as follows:

@defgroup MainGroup@brief ...@defgroup SubGroup1@brief ...@ingroup MainGroup@defgroup SubGroup2@brief ...@ingroup SubGroup1

The hierarchy in the "Modules" chapter isn't being respected by doxygen in the latex output (rendered as PDF): all the groups are treated as modules in the same level:

Modules  MainGroup  SubGroup1  SubGroup2

Any way to solve this?