[GAMEPLAY] The Dark Seal did not apply bonus AP.

While I was playing Ahri, I started off while "The Dark Seal", and few potions and a ward. I had been accumulating stack from assist and kills, however I did not get the bonus AP from the stacks. In the picture attached to this, shows that I had 10 stacks, but the item still said "15(+0) AP". This wasn't too frustrating, because I just bought a different item, however It may be a problem for other players, and myself in the future. Picture