Unlike Proudhon, Marx was long assumed to have opposed the cooperative movement. In this paper, the Author provides evidence that Marx declared himself decidedly in favour of labour-managed firms at various stages in his scientific activity. In Marx's opinion, cooperative firms were proof that mass production in line with the behest of modern science was possible even in the absence of a class of masters employing a class of hired workers. Marx looked upon cooperative firms as a new production mode arising spontaneously within the capitalistic production mode and capable of outperforming it. The passages of Marx's work in which these reflections are set out were completely forgotten because of the erroneous assumption that Marx was a straightforward enemy of the market and advocated its elimination forthwith after the enactment of a revolution. In point of fact, both Marx and Engels repeatedly emphasised that market economies would only be abolished at the end of a long process expected to give birth to a "new man".