The present invention relates to a method for stabilizing rotigotine, the method comprising providing a solid dispersion comprising polyvinylpyrrolidone and a non-crystalline form of rotigotine, wherein the weight ratio of rotigotine to polyvinylpyrrolidone is in a range from about 9:3.5 to about 9:6. The present invention also relates to a solid dispersion comprising a dispersing agent and a dispersed phase, said dispersed phase comprising rotigotine and polyvinylpyrrolidone, wherein the weight ratio of rotigotine to polyvinylpyrrolidone is in a range from about 9:3.5 to about 9:6, a pharmaceutical composition comprising such a solid dispersion, in particular a transdermal therapeutic system, as well as a method for the preparation thereof.