A wastegate assembly for a turbocharger includes a valve element having a valve body and a shaft extending away from the valve body. A spindle is coupled to the shaft for moving the valve element between a first and a second position to control the flow of exhaust gas to a turbine housing interior of the turbocharger. A washer is coupled to the shaft such that the spindle is disposed between the valve body and the washer for retaining the spindle to the shaft. A biasing member is disposed between the spindle and the washer, has a trough portion extending toward the spindle, and has a crest portion extending toward the washer. At least one of the spindle and the washer define a seating groove and the biasing member extends at least partially into the seating groove to seat and prevent rotation of the biasing member.