Issuee adding users with "-" in their username

Whenever a user with a "-" adds me as a friend, the link it provides to add them back gives me a "That is not a valid username." error.

This has occured three times, with the following users:

Dahaka-UK

Tedz-Revenge

Legendary-Elite

Said users can still be added by visiting their profiles and clicking the "Track This Person" link.