# OPF-042: file type not allowed in spine, how to fix it

Source: https://epubcc.com/epubcheck/opf-042/ (updated 2026-11-04)

EPUBCheck OPF-042 is an error message: “"…" is not a permissible spine media-type.” An EPUB 2 spine lists a file of a type that is never allowed in the spine, such as a stylesheet or an image. EPUBCheck names the media type; the spine is the reading order and only lists documents.

- Official message (EPUBCheck 5.4.0): "%1$s" is not a permissible spine media-type.
- Default severity: Error

## Typical causes

- An image added straight to the spine to show a full-page picture or a cover.
- A stylesheet listed in the spine by a tool that added every file.
- A spine copied from another book with different files.

## How to fix it

1. Find the itemref EPUBCheck points to.
2. For an image, create an XHTML page that shows it (an img element) and put that page in the spine instead.
3. For a stylesheet, remove the itemref; link the CSS from the XHTML documents instead.

## When it's not this

If the spine item is another non-standard type without a fallback, EPUBCheck reports OPF-043.

## Sources

- EPUBCheck 5.4.0 message texts (MessageBundle.properties, w3c/epubcheck on GitHub): https://github.com/w3c/epubcheck/blob/v5.4.0/src/main/resources/com/adobe/epubcheck/messages/MessageBundle.properties (read 2026-11-04)

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