moustache

Lengthening the beard and trimming the moustache

Q: In the Hadith a command is given to lengthen the beard and trim the moustache. I know that it is waajib to lengthen the beard, but what about the moustache? Is shortening the moustache also waajib? If not, then people argue and say that if you say that lengthening the beard is waajib, then trimming the moustache should also be waajib because they in the same Hadith.