# X_BACKFILL_SOURCE_INVALID

## Means

a backfill() declares both or neither of source and pages, or input with no scope

## Typical cause

backfill() declared source and pages together, neither of them, or an input schema with no scope(input) to key one pass per scope

## Fix

`backfill({ name, tenant, pages, handle }) with exactly one of source or pages, and scope: (input) => input.accountId beside input`

[Jobs](/error-codes#jobs)