A coupler for coupling an attachment to an excavator or other machine comprises a powered actuator for actuating a locking member into and out of said locking state, a first power coupling unit, and a second actuator for moving the power coupling unit into and out of an engaging position in which it is engagable with a corresponding second power coupling unit of the attachment. The coupler is configured to cause the first power coupling unit to move into the engaging position after said latching member adopts the locking state and, when decoupling the attachment from the coupler, to cause said latching member to remain in its locking state until after the first power coupling unit is moved out of its engaging position.