iOS: Font weight ignored when loading styles from multiple files

I am trying to load two styles (Regular and Light) of the same font (Open Sans) into a QML application.

The two styles come via TrueType files, from OpenSans-Regular.ttf and OpenSans-Light.ttf, which I load one after another (in the example I use FontLoader, but using QFontDatabase::addApplicationFont in C++ has the same effect).

After loading the font, I'm trying to specify the style to use from QML.

For Light:

font.family: "Open Sans"
font.weight: Font.Light

For Regular:

font.family: "Open Sans"
font.weight: Font.Normal

However, the font.weight statements are ignored by the font rendering. Instead of style used depends on the order the .ttf files are loaded:

If I load OpenSans-Regular.ttf first, all text items use regular/normal, when I load OpenSans-Light.ttf first, all items use light font.

This only affects iOS, on OS X the fonts are rendered differently, as specified in QML.

Example with font files attached.