In a prosthesis (600) comprising a first tubular graft (610) comprising a layer of graft material (619), at least one lumen (613) extending longitudinally therein, and a first fenestration (611) extending through the layer of graft material, a layer (612) of fenestration covering material is attached to the layer of graft material. The layer (612) is disposed in the lumen of the first tubular graft and partitions the first fenestration from the lumen of the first tubular graft. A first non-stented opening (625) is disposed proximal to the first fenestration and communicates with the first fenestration between the layer of graft material (619) and the fenestration covering material (612). In use, a proximal end of a second tubular graft (614) sealably engages the first non-stented opening, and the second tubular graft further extends through the first fenestration and into a branch vessel.
