A mobile crane comprising a main boom, which is supported on the mobile crane in such a way that the main boom can be rocked and which can be put upright by means of an elevating cylinder, and a main boom extension, which is releasably connected to a main boom head of the main boom by upper and lower pins. The main boom extension, proceeding from a home position, can be angled in relation to the main boom about a rocking axis by means of an angle drive after the upper pins have been released, which angle drive acts on a base of the main boom extension, where a drive of the mobile crane provided for a different task provides the kinetic energy for the angle drive. The angle drive is designed in such that a telescoping cylinder of the main boom provides the kinetic energy for the angle drive.