Reverting staged changes only unstages

When I try to revert staged changes using
Tools > Git > Current File > Undo uncommited changes, I get the output

Nicht zum Commit vorgemerkte Änderungen nach Zurücksetzung:
M	src/main.cpp
Cannot reset 1 file(s) in "/home/viengelm/Programming/tests/qtwebbrowser": 

09:54 Executing in /home/viengelm/Programming/tests/qtwebbrowser: /usr/bin/git reset HEAD -- src/main.cpp

which is the same output I get for unstaging. Interestingly, Qt Creator asks me if it should reload the file (as if it had been reverted), but the changes are still there after reloading.

I guess that the command unstages the file (which works despite the error message, as I mentioned in QTCREATORBUG-17156) but due to the error message, git doesn't return 0, so the reverting does not proceed.

If I run the command a second time, it works. Probably because the unstaging doesn't fail, since the file is already unstaged.