Making top pair on the river

[scooby]

I'm playing 5/5 and have about 600 in front of me. One limper in MP, I limp behind with J [img]/images/graemlins/spade.gif[/img] T [img]/images/graemlins/spade.gif[/img], CO limps, Button limps.

Flop comes down 4 [img]/images/graemlins/diamond.gif[/img] 8 [img]/images/graemlins/diamond.gif[/img] 9 [img]/images/graemlins/spade.gif[/img] BB bets out 20, limper calls, I call, CO folds, button calls, SB folds.

Turn is 2 [img]/images/graemlins/club.gif[/img]
Checked to me, I check, button checks.

River is J [img]/images/graemlins/club.gif[/img]
Checked to me, I bet 100.

Standard all the way through?