A heat exchanger for exchanging heat between first and second fluids, comprising first fluid channels extending in a longitudinal direction for carrying a first fluid, and second fluid channels extending in the longitudinal direction for carrying a second fluid, wherein the first and second fluid channels are arranged in an alternating pattern such that each of a plurality of the first channels is located laterally between second channels and each of a plurality of second channels is located laterally between first channels, and wherein the second fluid channels extend longitudinally beyond ends of the first fluid channels, and have ends that decrease in cross section such that the first fluid is able to pass around and between the ends of the second channels.