When condition example incomplete

On page 38, the book gives an example of the “when” conditions. The example is incomplete, according to IntelliJ code checking.
The error:

‘when’ condition must be exhaustive, add necessary ‘else’ branch.

The book’s code:

val race = “gnome”
val faction = when (race) {
“dwarf” → “Keepers of the Mines”
“gnome” → “Keepers of the Mines”
“orc” → “Free People of the Rolling Hills”
“human” → “Free People of the Rolling Hills”
}

Corrected:

val race = “gnome”
val faction = when (race) {
“dwarf” → “Keepers of the Mines”
“gnome” → “Keepers of the Mines”
“orc” → “Free People of the Rolling Hills”
“human” → “Free People of the Rolling Hills”
else → “Unknown Race”
}

Help me if I am missing something.