mkdirRecurse behaving strangly

[Trass3r]

I want to extract some files from a game archive providing path strings 
like "data/ai/campaign/leaders.csv".
So I tried mkdirRecurse to create the directory structure, this works 
fine but also creates folders named after the files, "leaders.csv" in 
this case.
So I added dirname:
mkdirRecurse(dirname(toUTF8(entry.filename)));

This doesn't work, telling that it can't create a folder that already 
exists.