Gr-osmosdr and rtl_tcp with local rtlsdr connected.

Hi all, I am trying to run multimode in grc and have it connect to a rtl_tcp server on another pc. (RaspberryPi) If I do this on a machine without local rtl-sdr that does work. If I run this at a pc which has also a local rtl-sdr it always chooses rtl device 0 and not the rtl_tcp server. Both systems run ubuntu 12.04 and the same grc and multimode versions. The commando used on both systems is python multimode.py --devinfo=rtl_tcp= 192.168.0.50:1234 Any hints how to solve this? Thanks, Ben