A machine (10) for manufacturing containers, includes a system (82) for providing assistance when changing moulds, including at least one module (84) which, combined with a moulding unit (24), has an actuation device (86) provided with an operating member (88) intended to cooperate with a member (52) for controlling the locking elements (55) when the moulding unit (24) occupies a specified reference position relative to the module (84), the operating member (88) being able to undergo a displacement so as to actuate the member (52) for controlling the locking elements (55) in order to cause the locking elements (55) to move towards at least one of the locked or unlocked positions and to make the mould holders (26) move towards at least one of the open or closed positions of the moulding unit (24).