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