Not an easy fold judging by the description of your villan. I think I might call here. I can only see two likely hands....J9 or heart draw. He may have smelt weakness with your 1/2 size pot bet and is making a play at you. I would make at least a 3/4 size pot bet. If the turn brings a blank and he checks I check and if he pushes i fold. If the river brings a blank and he pushes I call and if he checks I check.