# EPUBCheck CHK-003: Unrecognized custom message severity …

Source: https://epublab.com/epubcheck/chk-003/ (updated 2026-11-03)

EPUBCheck CHK-003 is an error message: “Unrecognized custom message severity "…" encountered in message overrides file "…".” The custom message file sets a severity EPUBCheck does not recognise.

- Official message (EPUBCheck 5.4.0): Unrecognized custom message severity "%1$s" encountered in message overrides file "%2$s".
- Default severity: Error

## Typical causes

- A typo in the severity name.

## How to fix it

- This is a problem with the file passed to EPUBCheck's -c (--customMessages) option, not with the EPUB. Fix the custom message file or run EPUBCheck without -c.
- To start from a correct file, run EPUBCheck with -l (--listChecks) to write the list of message IDs and their severities, then edit that list.

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EPUBLab.