QT.include (include javascript file in javascript file) does no longer work in QT 5.2

In my qml project I use a.js and z.js. a.js uses functions of z.js. So I included z.js with the following code in a.js:

Qt.include("z.js")

This worked perfectly with QT 5.1, but since I switched to 5.2 it doesnt work anymore. I get the following error:

a.js: TypeError: Property 'myExternalFunction' of object [object Object] is not a function

I attached an example which works with QT 5.1, but not with QT 5.2.