Herein described is a novel crystalline form of the hydrochloride of the (4- hydroxycarbamoyl-pheny3)-carbamic acid (6-dimethylamino methyl-2- naphtalenyl) ester. In particular, herein described is a polymorph of the hydrochloride of the (4- hydroxycarbamoyl-phenyl)-carbamic acid (6-dimethylamino methyl-2- naphtalenyl) ester, characterized by a Powder X Ray Diffraction spectrum as indicated in Figure 1, and/or by a DSC profile as indicated in figure 2, and/or by a TGA profile as indicated in figure 3 and/or by an IR spectrum as indicated in figure 4.