Design view of parent qml file no longer shows content of child qml file that uses import of c++ registered type

Register a type with qmlRegisterType in C++.
An import of this type in the main qml file is oke. The designer can handle that.
But if you add an extra qml file that does this import and you use this qml item in the main file, the designer shows nothing (height and width of item are 0). Setting them to a value results in an empty placeholder.
Running the application however renders the item correctly.

Also tried the Qt5.4 Beta and the same issue

This worked fine when I used Qt5.1.2