# X_FLAG_UNKNOWN

## Means

no flag is declared under this key

## Typical cause

a typo at the `isEnabled()` call site — answered as an error rather than a silent `false`, which would be a branch that never runs and never says so

## Fix

declare it with `defineFlag({ key: '<key>', … })`, or correct the key at the call site

[Flags](/error-codes#flags)