entities of imported module's submodule are not visible visible trough imported namespace

situation :

• module A (namespace 'http://a' revision '2016-01-01') includes submodule B which belongs to A, submodule B defines grouping service-data

• module C imports module A with namespace nsa
• using nsa:xyz is not resolved for module C and yang parser fails with error :

Error 10: Grouping '(http://a?revision=2016-01-01)service-data' was not resolved. [at /tmp/junit4915422298604003997/src/yang/C.yang:259:12]