An anti-drift mechanism for a downwardly oriented port rodder for cleaning a port opening of a recovery boiler. The anti-drift mechanism prevents a cutter of the rodder from accidentally drifting from a retracted holding position into the port upon the loss of holding power to the actuator. Two embodiments are disclosed. The first is a frictional engagement with the port rodder while the second involves the use of a valve in conjuction with the actuator to trap fluid pressure and maintain the rodder in the holding position.