AUTOUIC: Ninja needs two passes to correctly build Qt project

In a Qt project on Windows with set(CMAKE_AUTOUIC ON) and using the Ninja generator I experience that if a foo.ui is touched I need to build twice with Ninja. The first time ui_foo.h is produced. The second time foo.cpp is compiled (presumably because ui_foo.h is updated) and the program linked. With MinGW Makefiles foo.cpp is compiled the first time around. This is with CMake 3.7.2. This has been reproduced on Linux as well on master.