The invention comprises a door closer (1), a slide rail (3) and an arm (2). The arm is connected to the door closer (1) and to the slide rail (3). The slide rail is provided with a hold open device (4) in order to keep a door open. The arm (2) comprises an outer arm (8A, 9A) and an inner arm (8B, 9B). The inner is situated partly inside the outer arm in a sliding manner. The arm (2) also comprises a spring arrangement (11) in order to hold the inner arm (8B, 9B) in a normal position in the outer arm (8A, 9A), and a release device (10A, 10B). The release device is arranged to release the inner arm (8B, 9B) from its normal position when an external force being strong enough to active a release of the release device (10A, 10B) drives the inner arm (8B, 9B) out from the outer arm (8A, 9A).