Webengine renders black screen when locale is set (ANGLE)

I get a black screen where the browser widget is supposed to be when I set the locale to German (de-DE, others also do not work). If I skip this setting, or if I set it to others (examples: en-US, en-GB, zh-CN), the web page renders as expected.

I build qt locally on Windows 7, Visual Studio2015 SP2, using the Windows 10 SDK. However, I could not reproduce this with the precompiled version of Qt (official download, 5.6.1).
I configure with configure -confirm-license -opensource -nomake examples -nomake tests -debug-and-release -force-debug-info -platform win32-msvc2015

Attached you find a minimal example that reproduces the error.