Ryze Charm Bug

I was playing a game of League as Ahri against a Ryze mid. No big deal, all is normal, until I land my charm on him. He dashed at me. At first I was very confused and was sure I made a mistake, as if I had missed my charm or something. Unfortunately, it kept happening.

Basically, if Ahri charms Ryze while he's under the effects of his speed boost, he won't walk towards her, he'll run at full speed. From what I saw, he had the charmed particle effects and couldn't seem to take any action against me during the duration, but the fact that he closed the distance between us put me at a massive disadvantage. I assume this isn't supposed to be the case, seeing as how an ulting Master Yi is slowed by Ahri's charm.

tl;dr Ryze doesn't slow down while charmed Happens consistently and can be replicated

I'm assuming this is a bug, considering the Master Yi example has been accepted, I see no reason for Ryze to be immune to charm's slowing effects.