A method for manufacturing poly(2-hydroxyalkanoic acid) included the steps of a) mixing a cyclic diester of a 2-hydroxyalkanoic acid and a polymerization catalyst, b) polymerizing the cyclic diester to form poly(2-hydroxyalkanoic acid) in liquid phase, c) adding a phosphoric acid ester as a catalyst deactivating agent to the liquid phase, d) applying a devolatilization step to the liquid phase, and e) allowing the poly(2-hydroxyalkanoic acid) to solidify. The catalyst deactivating agent is added after the devolatilization step is applied. The method results in an improved melt stability of the manufactured polymer.