A valve unit comprises a valve (7) having a valve shaft (30) with a rotational axis, an actuator (6) having an atuator shaft (20) with a rotational axis, a mechanical coupler (1) for rotational coupling of actuator shaft and valve shaft, the mechanical coupler comprising a rotational axis (10) coinciding with the rotational axis of actuator shaft and the rotational axis of valve shaft, a first rotational member (2) coupled to actuator shaft and a second rotational member (3) coupled to valve shaft, and a bridge element (4), first and second rotational members having slots (21, 31) for receiving engagement pins (41) of the bridge element. The bridge element has a planar shape extending from first to second rotational member, and a body (42) and at least two engagement pins projecting from the body at each of two of its opposite ends in a parallel direction to the rotational axis of the mechanical coupler. The engagement pins are engaging with the corresponding slots in the rotational members. The planar bridge element comprises at least one through-hole (43) traversing the plane of the body of the bridge element.