Sudden health drops when undoing in shop

So, today I was playing Ori mid, and I had my whole inventory full with items, one of them being a mana potion. When I recalled, I thought about what to buy and sold the mana pot when I was still low life. Then I realized I couldnt buy anything for my next item, clicked the undo button and headed back to lane. However, when I undid, my health dropped to the amount I had when I first sold the mana pot, so I had to wait another 10 seconds to regenerate. This bug is pretty annoying, and I'd like to see it fixed.