# EPUBCheck OPF-012: Item property … is not defined for…

Source: https://epublab.com/epubcheck/opf-012/ (updated 2026-11-03)

EPUBCheck OPF-012 is an error message: “Item property "…" is not defined for media type "…".” A manifest item has a property that does not apply to its media type.

- Official message (EPUBCheck 5.4.0): Item property "%1$s" is not defined for media type "%2$s".
- Default severity: Error

## Typical causes

- cover-image on a file that is not an image, nav on a file that is not XHTML, or svg/mathml/scripted on a file that is not a content document.

## How to fix it

- Move the property to the right item or remove it. EPUBCheck names the property and the media type.

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