4-1 on the turn.. I think it's a call.
Also, what's wrong with getting it AI on the flop?

Anyway, he's keeping the pot small, and you have a hand with good show down value. A river blocking bet for 1/3 the pot, or a call if you think he's going to keep the pot small is +EV I think.

If he tries to make a huge river bet, folding is standard I think.