A closure piece for a powder syringe has a main body and a sealing element. The sealing element 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. A channel passes through the main body and the sealing element and has a proximal and a distal end. The closure piece includes a retaining element configured and/or disposed such that, prior to an activation of the powder syringe, any powder from a chamber of the powder syringe is at least substantially prevented from penetrating the channel when the closure piece is disposed in the closing position thereof on the powder syringe.
