[GAMEPLAY] Soraka's heal is allowing her to reduce herself to as low as 1hp

I've seen this a few times but in one situation lately when I played Soraka I was healing an ally and was very low on health. The last heal I threw at them took me down to 1hp and no that is not a typo. I was under the impression that you could not heal if it would reduce you below a set % (5%?) of your total HP. Clearly this is not working as intended because if I can reduce myself to 1hp that's way below the limit allowed.

How to reproduce it? I'm not positive I could reproduce to get to 1hp but to get very low it's quite easy.

Wait for an ally to take a lot of damage Heal them