A plate heat exchanger includes a stack of plate pairs with gaps between adjacent pairs, arranged to provide flow paths for a first fluid to pass through inner volumes of the plate pairs while simultaneously allowing a second fluid to flow over the outer surfaces of the plate pairs. At least one cylindrical fluid manifold for the first fluid extends through the plate pairs. A non-planar cap is arranged at one end of the plate heat exchanger to close off the cylindrical fluid manifold. A reinforcement plate is arranged at that end between the non-planar cap and an end plate of the plate heat exchanger. The position of the non-planar cap relative to a central axis of the cylindrical fluid manifold is maintained in order to prevent failure of the plate heat exchanger due to internal pressurization.