A Voltage Source Converter having at least one phase leg connected to opposite poles of a direct voltage side of the converter and comprising a series connection of switching cells has an arrangement configured to apply a pressure to opposite ends of stacks of semiconductor assemblies for pressing the assemblies towards each other so as to obtain electric contact between semiconductor assemblies in said stack while ensuring that the semiconductor assemblies of a first path of each switching cell of the converter go into a permanently closed circuit state in case of a failure of the respective switching cell. A second path of each switching cell has means configured to keep said second path including an energy storing capacitor non-conducting upon occurrence of a said failure.