Roll-up awning, includes a housing containing a rotatably mounted reel. The screen is wound on this reel and a front frame is fixed on its free extremity. At winding up, the front frame will be fed into a recess of the housing and then locked. Such a screen can be used on campers, where it is important that the front frame is locked in position when travelling. A locking device includes locking elements on the front frame and locking members on the storage reel. The locking members include a toothing which extends along the reel circumference and the locking include a lip or strip provided with a toothing. When the screen moves inwards the locking members and locking elements contact each other and lock the front frame.