Ahri Charm interrupts Malphite ult

I was playing a normal earlier today as Malphite and ulted toward an enemy Ahri. Mid-charge, she charmed me and I began walking slowly towards her as any other charmed unit would have. It clearly states in the tooltip for Malphite's ult that "Malphite cannot be interrupted by anything other than his own death", a situation that was clearly impossible because I started walking toward her (which obviously requires being alive).