Door Lock Won't Engage when Door is Open
 

I have a 2005 Civic EX 2-door w/o power locks & windows that I just bought from a private seller. Something that struck me as odd is that when I open the driver's side door I can't push down the button for the lock. When I'm sitting inside the car w/ the door shut I can lock it, and when I'm outside the car with the door shut I can lock it w/ the key. Has anyone experienced this before and can tell me what the issue is?

Thanks,
Mike