Johnson’s current contract with the Cottagers is set to expire at the end of the season, although talks over a new deal are ongoing.
“That’s not for me to make that decision,” Dempsey told the Fulham Chronicle.
“But AJ’s a goal scorer and he’s good to have around, and hopefully that will be the case for some time to come.
“He also likes to have a laugh and I respect him for the fact he’s had some tough injuries and fought back from them.”