The present invention relates to a method for providing modified gypsum plaster or filling compositions having reduced agglomeration in comparison to gypsum plaster or filling compositions comprising cellulose ether in a specific amount from 0.1 to 1.0 weight percent, based on the total dry weight of said composition. Also provided are dry mortars comprising cellulose ether, gelatin and gypsum for use in such methods, and gypsum-free mixtures comprising cellulose ether and gelatin which may be added to gypsum binder for use a for use in such methods.