QMessageBox wrong size on Android

Message boxes appear with wrong size on my android device.

Test1:
Uses a pointer to the parent window. The MessageBox is much to small. I can only see a few pixels on both my Android 4.1.2 tablet and on the 4.3 emulator. See attached screenshot.

Test2:
Without pointer to the parent window. The MessageBox appears too large. On my 4.1.2 table, the Ok button appears cropped on right screen border (only the left half of the button is visible). On the 4.3 emulator, the Ok button it not visible.

Test3:
The MessageBox appears fine on both devices.

Test4:
Works as expected. However, the setFixedSize() call has no effect when I provide a pointer to the parent window.