[Gameplay] no movement speed with aether wisp ANIVIA

I noticed that I don't get additional 5% movement speed when I buy aether wisp. I get the movement speed when I complete the full item though. It's either a small but annoying bug or my lack of knowledge. Thanks.

EDIT: i realzied that this only occurs with Anivia. Please fix it riot! It is really annoying to be denied this movement speed :/