A lock mechanism for a dispenser in combination with an exchangeable roll of material is provided, wherein the roll includes at least one end plug with a bearing pin for mounting the roll to the lock mechanism. The lock mechanism comprises a lock housing with a guide slot for insertion of the bearing pin. The guide slot has a first section with a first width and a second section with a second width which is smaller than the first width. First and second sections are arranged in a direction perpendicular to the longitudinal extension of the guide slot and in a longitudinal direction of the bearing pin. A sliding element is mounted to the lock housing and movable between a first position closing or narrowing the width of the guide slot and a second position opening the guide slot. A lock element is mounted to the sliding element and is rotationally movable about an axis of rotation between a locked position and an unlocked position. The lock element has an engagement portion which, in a locked position, is engaged with a locking geometry of the lock housing.