A device for expanding a tubular elastic body, the device comprises a rigid tube to be introduced into at least a part of the elastic body and keep the elastic body in an expanded state, and an expansion means adapted to expand the elastic body and arranged to be introduced into a first end of the rigid tube. The expansion means is adapted to be movable inside the rigid tube and when the expansion means is fully introduced in the rigid tube, the expansion means protrudes at a second end of the rigid tube and thereby forms a transition between the rigid tube and the expansion element. One end of the expansion means is provided with a radially resilient expansion element with a width decreasing in the introduction direction of the expansion means into the first end of the rigid tube.