Johnny Gat Quest - Assassinate Julius Little GLITCHED! Is there a fix?

[Matthis]

Of the quests that Johnny offers for you to complete, I have to assassinate Julius Little for a part of one. When I go to the area that Julius is supposed to spawn (as a "target" -- it says to wait for the target) the objective never completes even though Julius appears. When I kill him, the quest isn't complete and still asks me to wait for the target to appear. Is there a fix to this?