Gameplay bug, Pantheon's passive and Dragon

So I wanted to see how early Pantheon could do dragon on patch 4.21, however after killing Grump and taking blue, with my passive up I went for a level 2 dragon. The passive worked fine versus Grump and Golem, but Dragon's auto attacks ignored the passive. I'm actually afraid to take him in game. I tried it blue side first, then I tried it red side, no difference. I don't know if it's a factor but both times I used the Full Metal Pantheon skin.

Thanks for all that you do, Rhett