Manamune - AD not scaling with mana [GAMEPLAY]

While using Jayce on Summoners Rift I build Manamune . After I fist purchased it it scaled my AD to mana correctly to where I was at. (Displaying I had +21 AD) After I build more mana items and manamune transformed into I checked to see why I was dealing as much dmg as I should be only to notice that my bonus AD was still at +21. I then tested it by buying and watching to see if it was which the text... but to my despair I didn't see an increase in my AD.. :(

Hope you see this!

Thanks