Kogmaw damage vs towers level 1

When Kog attacks towers with a level 1 Bio-Arcane Barrage, it does ~25% the damage it should. Eg: My normal attacks were doing 36 damage, with bio on, it was doing 8 damage. This seemed to fix itself at level 3 of Bio Arcane Barrage (did not test level 2): ~108 damage normal, 66 after.