An anti-scatter device (10) for an X-ray detector (100) is provided. The anti-scatter device (10) comprises an anti-scatter grid (12) with a plurality of slats (13) for absorbing X-rays and a cover element (14, 14a) arranged on a side (17a) of the anti-scatter grid (12), wherein ends (16a) of the slats (13) are coupled to the cover element (14, 14a), and the cover element (14, 14a) comprises an electroactive polymer material. A dimension of the cover element (14, 14a) is changeable by applying a voltage to the electroactive polymer material, such that a distance between the ends (16a) of the slats is changeable by applying the voltage.