Insomnia

This Pokémon cannot be asleep.

This causes Rest to fail altogether. If a Pokémon is asleep and acquires this ability, it will immediately wake up; this includes when regaining a lost ability upon leaving battle. Yawn will fail if used against this Pokémon, and if it acquires this ability while drowsy it will not fall asleep.

This ability functions identically to Vital Spirit in battle.