Olaf "Rage" Passive?

I was Playing olaf top with Ignite and Ghost, And i noticed that when i would basic attack something i would gain movement speed, and in the area of the screen where it shows passives, a little ghost icon would pop up titled Rage, and id have extra movement speed for about 2 seconds, did i miss a patch or something with Olaf or is this a bug?

My build was, titanic hydra/ frozen mallet/Greaves/ black cleaver/warmogs/ and brok