A well established belief both in the game-theoretic IO and in policy debates is that market concentration facilitates collusion. We show that this piece of conventional wisdom relies upon the assumption of profit-seeking behaviour, for it may be reversed when firms pursue other plausible goals. To illustrate our intuition, we investigate the incentives to tacit collusion in an industry formed by Labor-Managed (LM) enterprises. We characterize the perfect equilibrium of a supergame in which LM firms play an infinitely repeated Cournot game. We show that the critical threshold of the discount factor above which collusion is stable (i) is lower in the LM industry than in the capitalistic one; (ii) monotonically decreases with the number of firms.