The American's lengthy stay at Craven Cottage ended on a sour note, with the west Londoners' supporters booing him when the teams met earlier in the season.
"Of course you hope that it doesn't happen again because he did a lot for the club as well," Dembele said. "Let's concentrate on the game.
"It was a very good time at Fulham. I enjoyed it a lot.
"They gave me a lot of confidence. They were behind me all the time so I had a very good experience there and I have a very good feeling about the club."