Unable to save screenshot in non user-owned directory

Starting with 4f7581e0 saved screenshots now end up as empty files when saved in the following location:

SHARED on /media/sf_SHARED type vboxsf (rw,nodev,relatime,iocharset=utf8,uid=0,gid=109,dmode=0770,fmode=0770,tag=VBoxAutomounter)

Version: git master (cabe6ebd)