AQo unimproved, bet or check behind on 5th street flush card?

[belloc]

Is this an obvious river bet in position here, or is a check behind okay with the scary river card? I have less than two orbits on the villain in MP1, but he's played about half those hands and not yet raised a pot. No reason to believe he's being tricky here, but any pair wins for him, even the river club doesn't make him his flush.

Party Poker 2/4 Hold'em (8 handed) converter

Preflop: Hero is MP2 with Q[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/spade.gif[/img].
<font color="#666666">2 folds</font>, MP1 calls, <font color="#CC3333">Hero raises</font>, CO calls, <font color="#666666">3 folds</font>, MP1 calls.

Flop: (7.50 SB) 3[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
MP1 checks, <font color="#CC3333">Hero bets</font>, CO folds, MP1 calls.

Turn: (4.75 BB) 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
MP1 checks, <font color="#CC3333">Hero bets</font>, MP1 calls.

River: (6.75 BB) 2[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
MP1 checks, Hero checks.

Final Pot: 6.75 BB