"death.attack.genericKill.player" displays raw translation string (is untranslated)

The death message "death.attack.genericKill.player" is untranslated.

How to reproduce:

1. Summon a hostile mob and let it attack you.
2. Use /kill.

What I expected to happen was:

A death message that would show how I died.

What actually happened was:

A death message that is nonsensical for most casual players.