A closure piece for a powder syringe is proposed, having a main body, a sealing element, which is disposed on the main body such that it rests in a sealing manner against a distal opening of a powder syringe, when the closure piece is disposed in the closing position thereof on the powder syringe, and a channel, which passes through the main body and the sealing element and has a proximal and a distal end. The closure piece is characterized by a retaining element, which is configured and/or can be disposed such that, prior to an activation of the powder syringe, any powder from a chamber of the powder syringe is at least substantially, preferably completely, prevented from penetrating the channel, when the closure piece is disposed in the closing position thereof on the powder syringe.
