The 'Install from zip file' option is missing

Hi,
I have downloaded a ZIP-file with add-on's that I want to add to XBMC.
I go to Go to System > Settings > Add-ons. Now I should get the 'Install from zip file' option, but I cannot find it.
All I get is a list of add-ons in the default repository.
What I am I doing wrong?
Cas