Fitting for a sliding door with breakout functionality, comprising an upper fitting unit, which is guided in a ceiling guide of the fitting, and a lower fitting unit, which is guided in a floor guide of the fitting, for guiding a door wing of the sliding door during normal operation along a first sliding direction and an opposite second sliding direction, wherein, in the breakout situation, the fitting units (40, 50) allow the door wing of the sliding door to be pivoted upwards about an axis of rotation defined by the fitting units (40, 50), wherein the fitting has a locking device for the form- and/or force-fitting locking of the lower fitting unit in the floor guide against a movement in the first sliding direction and/or the second sliding direction in the breakout situation, characterized in that the locking device has a toothing extending in the floor guide along the sliding directions (300, 400) and a blocking element, which is rotatably mounted in the lower fitting unit and is adapted to the toothing and can be mechanically operatively connected to the door wing in such a way that pivoting of the door wing upwards in the breakout situation leads to rotation of the blocking element, as a result of which the blocking element engages in the toothing and thus the lower fitting unit is locked with a form fit in the floor guide, wherein: - the blocking element for engaging in the toothing has a blocking edge with an angle of 80° to 100°, wherein the blocking edge is adjoined by a sliding side of the blocking element, which sliding side, during normal operation, is aligned parallel to the sliding directions (300, 400), or - wherein the toothing has a rack and the blocking element has a pinion matching the rack, wherein a pinion section of the pinion that faces the rack during normal operation is equipped with a toothless sliding side; and in that the sliding side and/or a pinion hub of the pinion forms part of the guide of the door wing along the sliding directions (300, 400) during normal operation. in that the locking device has a toothing extending in the floor guide along the sliding directions (300, 400) and a blocking element, which is rotatably mounted in the lower fitting unit and is adapted to the toothing and can be mechanically operatively connected to the door wing in such a way that pivoting of the door wing upwards in the breakout situation leads to rotation of the blocking element, as a result of which the blocking element engages in the toothing and thus the lower fitting unit is locked with a form fit in the floor guide, wherein: - the blocking element for engaging in the toothing has a blocking edge with an angle of 80° to 100°, wherein the blocking edge is adjoined by a sliding side of the blocking element, which sliding side, during normal operation, is aligned parallel to the sliding directions (300, 400), or - wherein the toothing has a rack and the blocking element has a pinion matching the rack, wherein a pinion section of the pinion that faces the rack during normal operation is equipped with a toothless sliding side; - the blocking element for engaging in the toothing has a blocking edge with an angle of 80° to 100°, wherein the blocking edge is adjoined by a sliding side of the blocking element, which sliding side, during normal operation, is aligned parallel to the sliding directions (300, 400), or - wherein the toothing has a rack and the blocking element has a pinion matching the rack, wherein a pinion section of the pinion that faces the rack during normal operation is equipped with a toothless sliding side; and in that the sliding side and/or a pinion hub of the pinion forms part of the guide of the door wing along the sliding directions (300, 400) during normal operation.