A carrier assembly for an operating unit of an agricultural machine includes a carrier arm, a suspension system for suspending an operating unit from the carrier arm and a mounting structure for mounting the carrier arm on a carrier vehicle. A pivot mechanism enables pivoting movement of the carrier arm relative to the mounting structure, and a first actuator drives pivoting movement of the carrier arm between a working position and a transport position. The carrier assembly includes a releasable locking mechanism for locking the carrier arm in the transport position. The locking mechanism includes a first locking element carried by the mounting structure and a second locking element carried by the carrier arm, which is engageable with the first locking element when the carrier arm is in the transport position.