A drilling motor assembly can include a housing, a shaft, and a pawl which selectively engages a recess, the pawl having an axis of rotation and a generally planar engagement face which engages a generally planar engagement face of the recess when relative rotation between the housing and the shaft is prevented. The engaged engagement faces can be oblique relative to a radius extending from the axis of rotation to the engaged engagement faces. A method of drilling a wellbore can include flowing a fluid through a drilling motor assembly, thereby rotating a shaft relative to a housing, and rotating the housing, thereby engaging a pawl with a recess and preventing relative rotation between the housing and the shaft, the pawl and recess each having a generally planar engagement face, whereby the engaged engagement faces prevent relative rotation between the shaft and the housing.