Lisbie joined Charlton as a trainee in 1995

Lisbie, 28, has been training with the U's during the summer after being released by the Addicks after 12 years at the end of last season.

He has featured in three pre-season friendlies, scoring in one of them.

Lisbie struggled to hold down a regular spot at The Valley, starting fewer than 90 matches and making more than 100 substitute appearances.