{,} not working in Ubuntu

Musescore (2.0 and 2.0.1, Ubuntu 12.04 and 14.04, 32 and 64 bit, kxstudio download and own compiled versions) does not recognize { and } for Decrease/Increase stretch on a german (AltGr-7 , AltGr-0) keyboard. Same problem on Swiss keyboard (AltGr-ä, AltGr-$). It is not even possible to enter these characters in the Preferences->Shortcuts menu.

However, {} can be entered in Lyrics, Title, Composer,.. fields.

On Win7, { and } work as expected with the same keyboards.