On to the river...

River: ($21.85) 6 (2 players)
Hero checks, Button bets $3.50, Hero ?

This has to be a clear call based on the way I played the hand (correctly or incorrectly). I can't fold when I have roughly 8 to 1 odds, can I? Besides that, his bet smells pretty weak to me. If he had it, he would have pushed by now...