Dying to a TNT Minecart ignited by a Creeper doesn't count as the Creeper's kill

Steps to Reproduce:
1) Hold a totem and place a rail and a TNT minecart on it
2) Summon a Creeper and use the totem on the creeper which then causes the TNT minecart to fizz
3) Die to the minecart

Expected Result:
"Player was blown up by Creeper"

Observed Result:
"Player blew up"