[Gameplay] [5% CDR MASTERY NOT WORKING]

Hello, I have been playing Gangplank for a few weeks now and I always use 5% CDR Mastery but it seems that it doesnt work at all in-game right now and yes I have checked my masteries multiple times and tested it through games. If I wasn't maining any champion with high cdr I wouldn't be mad at all but this one is painful I could have survived,and got kills multiple times and it was just .1 second away ;-; Anyways I have reported this bug but I just want to let people know that this bug exists and don't have to waste their time for reporting this bug. ^_^