Dean Smith has bemoaned the decision to disallow Konstantin Kerschbaumer's goal, believing it should have been allowed to stand.
Brentford had led through Sergi Canos before the break but Sean Morrison levelled soon after half-time.
The Austrian thought he'd put the Bees in front but the whistle had gone for what is believed to be hand ball.
And the decision came back to haunt Brentford as Peter Whittingham fired home the winner 15 minutes from time.
“I don't know why Kersch's goal was disallowed and it's a crying shame that we lost today,” Smith said.
“I've watched it back and the whistle doesn't go until it hits the net. I'm not sure whether he was thinking it was handball and then I'd better give it as they've scored.
“There looked nothing wrong to me. Sergi backed into Morrison. Morrison is trying to win it.
“There's no ball to hand. It's ricocheted. Lasse gets a shot in. It comes back to Kersch and he finishes it.”
