---
title: "TYPO3 Exception 1478105826"
manual: "TYPO3 Exceptions"
version: "main"
permalink: "https://docs.typo3.org/permalink/t3exceptions:typo3-exception-1478105826"
source: "Exceptions/1478105826.rst"
modified: "2026-09-16T07:39:08+00:00"
---

# TYPO3 Exception 1478105826

> [!NOTE]
> Below, the TYPO3 community may have provided additional information or
> solutions for this exception. However, these may or may not apply to your
> particular case. If you can provide more information, you should come back
> here and add your experience and solution steps to this issue once you have
> resolved it.
>
> General TYPO3 troubleshooting tips can be found in the *Troubleshooting*
> section in the menu. You can also ask questions and receive support in the
> [TYPO3 Questions category on talk.typo3.org](https://talk.typo3.org/c/typo3-questions/).
>
> To add your experience, click "Edit on GitHub" above and follow the
> ["Edit on GitHub" workflow](https://docs.typo3.org/m/typo3/docs-how-to-document/main/en-us/Howto/EditOnGithub.html#docs-contribute-github-method).
> Also check out
> [our tip on Coding Style and reST](https://docs.typo3.org/permalink/t3exceptions:tip-about-rest-coding-style).

## FlexForm location was not found, TYPO3 12.0

```none
Data structure file "EXT:my_extension/Configuration/FlexForms/NotExisting.xml" could not be resolved to an existing file
```

When opening a plugin in the backend and the referenced FlexForm is missing.

### Solution

Correct the path to the flexform in method `ExtensionManagementUtility::addPiFlexFormValue()`, which is usually called in
`EXT:my_extension/Configuration/TCA/Overrides/tt_content.php`.

## Using `$_EXTKEY` in configuration files in TYPO3 v9 and above

This error can happen when using the variable `$_EXTKEY` in a TCA
definition like `Configuration/TCA/Overrides/tt_content.php` without
defining it. In TYPO3 versions before 8 the variable was automatically
defined.

### Solution

Replace all occurences of `$_EXTKEY` with the extension's name or
define the variable locally.