A slip joint for a riser between a well and a floating petroleum installation, for example an oil platform. The slip joint includes, an outer pipe and an inner pipe, the pipes arranged to enable telescopic movement relative to one another in order to compensate for a change in distance between the sea bottom and the platform. The inner pipe is connected to a piston, the piston being operable in response to hydraulic pressure for inflicting a tensile force on riser. The outer diameter of the inner pipe is adapted to the diameter of outer pipe so as to form an annulus between the pipes. The piston is fixedly connected to inner pipe at or close to a downwardly directed end thereof, the annulus and the piston being subjected to hydraulic pressure. A protective sleeve is provided below the piston, which is slippingly arranged within outer pipe.