Nailgun not displaying in {weapon} variable of messages

Some of my botrespawn NPCs are equipped with nailguns. When they kill a player using a nailgun, this is what appears in chat:

Crate Defender Slider rubbed out Kalon with a {weapon} from 8.1 meters away.
Nailgun appears to be defined as a weapon in the config file:
"Nailgun": "Nailgun",
Should this instead be set as:
"pistol.nailgun": "Nailgun",

?

Mine is listed as

"Nailgun": "Nailgun",

and it records the deaths ok , just tested it with this result.