QVFB doesn't compile in current 4.8 git

Trying to build QVFB in current 4.8 git on Linux/X11 results in

g++ -Wl,-rpath-link,/usr/src/ark/BUILD/qt/lib -m64 -Wl,-O1 -o ../../bin/qvfb .obj/release-shared/qvfb.o [...] .obj/release-shared/qrc_qvfb.o -L/usr/src/ark/BUILD/qt/lib -L/usr/X11R6/lib64 -lpng -lz -lXtst -lQtOpenGL -L/usr/src/ark/BUILD/qt/lib -L/usr/X11R6/lib64 -lQtGui -lQtCore -lGL -lpthread -lXi -lXrender -lXrandr -lXfixes -lXcursor -lXinerama -lfontconfig -lfreetype -lXext -lX11 -lm
.obj/release-shared/qwssignalhandler.o: In function `QWSSignalHandler::clear()':
/usr/src/ark/BUILD/qt/tools/qvfb/../../src/gui/embedded/qwssignalhandler.cpp:99: undefined reference to `QWSLock::~QWSLock()'
collect2: ld returned 1 exit status