A system with which a correction of the fuel composition upon a change in the state of load of an internal combustion engine with which a mixture-forming device (4, 6, 8, 9, 11) is associated is constructed in structurally simple manner. The mixture-forming device has a feed unit (6) for the fuel with an inlet-side fuel conveyor line (5) and a discharge-side fuel conveyor line (7) and a movably mounted feed member (18). Depending on the position of the feed member (18), the feed member (18) provides variable fuel passage cross-sections in the feed unit (6). The feed unit is connected via an opening (31) which is closed in sealing fashion by a movable equalization element (33), the equalization space (32) being connected via a branch line (34) to the discharge-side fuel conveyor line. The feed member and the equalization element are coupled with each other locked for movement in such a manner that a movement of the feed member in the direction of an enlarged fuel passage cross-section leads to a movement of the equalization element which reduces the equalization space. A movement of the feed member in the direction of a reduced fuel passage cross-section leads to a movement of the equalization element which enlarges the equalization space.