What would he make the river raise with?

[iceman5]

$2/$4 NL at Prima
2 limpers and then I raise to $20 with KK. Both limpers call.
I have $400, they have $400 and $350 or so.

The pot is $65. The flop is Q42 with 2 spades. Its checked to me and I bet $50. UTG calls and the other guy folds.

Pot is $115. The turn is another 2. He checks and I check behind.

Pot still $115. The river is a 6. He checks. I bet $50 and then he check raises all in. The flush didnt get there.

I checked behind at the turn so if he has a real hand you would think he has to make a value bet at the river right?

Do you call this? The raise is about $250 to me and the pot is about $465