The invention relates to an immobilizing device for a toothed wheel suitable for the field of horology where it can be part of a direct- or indirect-impulse escapement, in particular in a wristwatch. This immobilizing device (1, 2, 3, 4, 5, 6) comprises: —a base (7); —an immobilizer (9) comprising two arms (10, 11) each provided with a pallet (14, 15) intended to come into contact with a tooth of the toothed wheel (40); —a first and a second elastic element (12, 13) each having an end connected to the immobilizer (9) and another end connected to the base (7); —a third elastic element (16) connected to the immobilizer (9), and it has the particular feature that it is in one piece or in one piece apart from at least one of the pallets (14, 15). The invention also relates to a timepiece and to a method for assembling such a timepiece.