Strange error when compiling back without gsc

[BALATON Zoltan]

Hello,

I've tried to compile gnustep-back using x11 and gslib without the gsc
directory (by removing gsc from SUBPROJECTS in Source) as the gslib
backend replaces gsc but after this programs are producing the following
error:

/home/test/build/Calculator/Calculator.debug/ix86/linux-gnu/gnu-gnu-gnu/Calculator:
Uncaught exception NSInvalidArgumentException, reason:
XGServer(instance) does not recognize _setupRootWindow

This is strange because the above method is both defined and called in the
x11 server code which is correctly compiled in. If I add gsc back to
SUBPROJECTS everything is working. I have no clue what could be wrong.
Could someone please explain what am I missing?

Thank you,
BALATON Zoltan