# MED_013: overlay never cites chapter, how to fix it

Source: https://epubcc.com/epubcheck/med_013/ (updated 2026-11-04)

EPUBCheck MED_013 is an error message: “Media Overlay Document referenced from the "media-overlay" attribute does not contain a reference to this Content Document.” A chapter's media-overlay attribute names a SMIL file that never refers to that chapter. The overlay must contain text elements pointing to the chapter it narrates, otherwise the reading app has nothing to synchronise.

- Official message (EPUBCheck 5.4.0): Media Overlay Document referenced from the "media-overlay" attribute does not contain a reference to this Content Document.
- Default severity: Error

## Typical causes

- The media-overlay attribute set on the wrong manifest item.
- A SMIL file whose text src paths still point to old file names.

## How to fix it

1. Open the SMIL file named by the attribute and check the src of its text elements.
2. Correct the paths so they point to the chapter, or set the attribute to the overlay that really narrates it.
3. Rebuild the EPUB and run EPUBCheck again to confirm the message is gone.

## When it's not this

If the overlay refers to the chapter but the attribute names another overlay, see MED_012.

## Sources

- EPUB 3.3, §9.3.5.1 Including media overlays: https://www.w3.org/TR/epub-33/#sec-package-including (read 2026-11-04)

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