The present invention relates to a process for the treatment of a cellulosic molded body, wherein the molded body is contacted with an acid solution of a chitosan. The process according to the invention is characterized in that the chitosan has a deacetylation degree of at least 80%, a nitrogen content of at least 7 w %, preferably at least 7.5 w %, a weight average molecular weight Mw (D) of 10 kDa to 1000 kDa, preferably 10 kDa to 160 kDa, and a viscosity in 1 w % solution in 1 w % acetic acid at 25° C. of 1000 mPas or less, preferably 400 mPas or less, in particular preferably 200 mPas or less.
