Extension module for enlarging an interior of a vehicle by partially shifting an outer wall delimiting the interior, having the following features: a. the extension module comprises an extension box, which has an end wall and four side walls, wherein the end wall forms a shiftable wall portion of the outer wall and is provided for arrangement in a cutout in a positionally fixed wall portion of the outer wall, and b. the extension box is shiftable in an extension direction between a storage position and a use position by means of an extension system, - wherein, in the storage position, the shiftable wall portion together with the positionally fixed wall portion forms a substantially flush surface and the side walls are arranged in the interior, and - wherein, in the use position, the shiftable wall portion is extended in the extension direction in relation to the positionally fixed wall portion and the side walls form part of the outer wall, c. the extension system comprises at least one scissors fitting which is arranged in an inner region and has a first fastening portion for attaching to the extension box and has an opposite second fastening portion for attaching in a fixed position to the positionally fixed wall portion of the outer wall, and d. the scissors fitting comprises two pivot levers (72, 74) which are connected in an articulated manner to each other and which are each attached pivotably at one end to one of the fastening portions (62, 64) and of which at least one pivot lever (72, 74) is guided at its other end in translation on the opposite fastening portion (64, 62), and e. the at least one scissors fitting is arranged between an inner side of the positionally fixed wall portion, on the one hand, and the extension box, on the other hand, and therefore the extension box can be transferred into its use position by means of a force loading the fastening portions (62, 64) towards each other, f. the scissors fitting has at least one main actuator (66, 68) which acts on at least one end (72C, 74C), which is guided in translation, of at least one pivot lever, characterized by the following further features: g. the scissors fitting additionally has at least one starting actuator which can act upon at least one of the pivot levers (72, 74) in such a manner that the fastening portions are subjected to a force in a direction away from one another, and h. the starting actuator is designed for bidirectional operation, and therefore the starting actuator can act upon the at least one of the pivot levers (72, 74) in such a manner that the fastening portions (62, 64) are pulled towards each other. a. the extension module comprises an extension box, which has an end wall and four side walls, wherein the end wall forms a shiftable wall portion of the outer wall and is provided for arrangement in a cutout in a positionally fixed wall portion of the outer wall, and b. the extension box is shiftable in an extension direction between a storage position and a use position by means of an extension system, - wherein, in the storage position, the shiftable wall portion together with the positionally fixed wall portion forms a substantially flush surface and the side walls are arranged in the interior, and - wherein, in the use position, the shiftable wall portion is extended in the extension direction in relation to the positionally fixed wall portion and the side walls form part of the outer wall, - wherein, in the storage position, the shiftable wall portion together with the positionally fixed wall portion forms a substantially flush surface and the side walls are arranged in the interior, and - wherein, in the use position, the shiftable wall portion is extended in the extension direction in relation to the positionally fixed wall portion and the side walls form part of the outer wall, c. the extension system comprises at least one scissors fitting which is arranged in an inner region and has a first fastening portion for attaching to the extension box and has an opposite second fastening portion for attaching in a fixed position to the positionally fixed wall portion of the outer wall, and d. the scissors fitting comprises two pivot levers (72, 74) which are connected in an articulated manner to each other and which are each attached pivotably at one end to one of the fastening portions (62, 64) and of which at least one pivot lever (72, 74) is guided at its other end in translation on the opposite fastening portion (64, 62), and e. the at least one scissors fitting is arranged between an inner side of the positionally fixed wall portion, on the one hand, and the extension box, on the other hand, and therefore the extension box can be transferred into its use position by means of a force loading the fastening portions (62, 64) towards each other, f. the scissors fitting has at least one main actuator (66, 68) which acts on at least one end (72C, 74C), which is guided in translation, of at least one pivot lever, g. the scissors fitting additionally has at least one starting actuator which can act upon at least one of the pivot levers (72, 74) in such a manner that the fastening portions are subjected to a force in a direction away from one another, and h. the starting actuator is designed for bidirectional operation, and therefore the starting actuator can act upon the at least one of the pivot levers (72, 74) in such a manner that the fastening portions (62, 64) are pulled towards each other.