Changes in header file not taken into account by clang code model

How to reproduce:

1) Create new widgets project
2) Add a signal handler/slot using designer
3) The handler is implemented but the code in the cpp file (form.cpp)
will never get valid. Apparently the code uses an older version of form.h.

Step 2 does is not necessarily related to the designer. Adding a method manually also triggers the issue.

After saving the header file (form.h) the issue seems to be gone.
If I close and reopen the project I see a similar issue for added methods in form.cpp until I save form.h once.