The present invention relates to a machine (10) for manufacturing containers, which includes a system (82) for providing assistance when changing moulds, comprising 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 means (55) when the moulding unit (24) occupies a specified reference position relative to the module (84), said operating member (88) being able to undergo a displacement so as to actuate said member (52) for controlling the locking means (55) in order to cause the locking means (55) to move towards at least one of said locked or unlocked positions and to make the mould holders (26) move towards at least one of said open or closed positions of the moulding unit (24).