The invention refers to a plate package for a plate heat exchanger, a method for manufacturing a plate package, a use of a plate package, and a plate heat exchanger. The plate package includes a plurality of heat exchanger plates (1), which are stacked on each other and which each includes a number of portholes. The plates (1) are compression molded and permanently connected to each other in a number of joints in such a manner that the plates between each other form a first passage for a first fluid and a second passage for a second fluid. The plate package is designed to permit at least one of the fluids to flow through the respective passages at a predetermined maximum working pressure. The plate package has an increased strength achieved by subjecting at least one of the passages to at least a local inner plastic deformation of the plate package.