Error with update

When executing this:
sudo port -v upgrade outdated

I get this:
Can't map the URL 'file://.' to a port description file (Could not
find Portfile in .). Please verify that the directory and portfile
syntax are correct.
Error: To use the current port, you must be in a port's directory
Error: No port  found.

While:
sudo port -v selfupdate works fine.

Suggestions?