The invention relates to a process for reducing the sagging of a gypsum-based element, such as a gypsum board. This process comprises the introduction into the gypsum-based composition, before the setting and hardening of the latter, of tartaric acid or tartaric acid salt(s), in a quantity greater than 0.001% by weight with respect to the weight of the calcium sulphate semihydrate contained in the gypsum-based composition. The invention also relates to a gypsum-based composition for such an element. This composition comprises, in percentages by weight with respect to the weight of the calcium sulphate semihydrate in the composition, from 0.003% to 0.45% of tartaric acid or tartaric acid salt(s) and from 0.05% to 0.95% of boric acid or boric acid salt(s). Finally, the invention also relates to a gypsum-based element with reduced sagging, obtained by hydraulic setting and hardening of a composition according to the invention, the use of tartaric acid or tartaric acid salt(s) for reducing the sagging of a gypsum-based element as well as a process for manufacturing a gypsum-based element with reduced sagging.