4-Line PS Script Error (Changing PaintingCursor)

Hi, does anyone know what's wrong with this code?

if (app.preferences.paintingCursors == PaintingCursors.STANDARD){ 
    app.prefences.paintingCursors = PaintingCursors.BRUSHSIZE; } 
else if (app.preferences.paintingCursors == PaintingCursors.BRUSHSIZE){ 
    app.prefences.paintingCursors = PaintingCursors.STANDARD; } 

 I get "undefined is not an object" in line 2 (and therefore in 4 aswell)..

Any Ideas?

Regards, Jakob