A longitudinal adjuster may have a first transverse locking bar accommodated in a slot of a first seat rail. A spindle may be guided through an opening of the first transverse bar in a contact-free manner. At a distance from the first transverse locking bar toward the front, a shoulder of the spindle is arranged. In reaction to a specified action of force, the first transverse locking bar is clamped between the first seat rail and the shoulder. As a result, a force from the first seat rail via the first transverse locking bar, the shoulder, the spindle, and the spindle nut can be diverted to the second seat rail.