Problem adding ppa:ubuntugis-unstable

I'm trying to add the ppa:ubuntugis/ubuntugis-unstable repository to my ubuntu. I type:

sudo add-apt-repository ppa:ubuntugis/ubuntugis-unstable

And I'm getting:

Cannot add PPA: 'ppa/ubuntugis/ubuntugis-unstable'. 
Please check that the PPA name or format is correct.

I can ping ppa.lauchpad.net and apt is working (just did an upgrade). Can anyone spot what is wrong?