---
title: "Deprecation: #104789 - Fluid variables true, false, null"
manual: "TYPO3 Core Changelog"
version: "main"
permalink: "https://docs.typo3.org/permalink/changelog:deprecation-104789-1725196704"
source: "Changelog/13.3/Deprecation-104789-FluidVariablesTrueFalseNull.rst"
typo3-version: "13.3"
typo3-major: 13
type: "deprecation"
issue: 104789
forge: "https://forge.typo3.org/issues/104789"
tags: ["Fluid", "NotScanned", "ext:fluid"]
rendered: "2026-09-23T16:35:56+00:00"
---

# Deprecation: #104789 - Fluid variables true, false, null {#deprecation-104789-1725196704}

See [forge#104789](https://forge.typo3.org/issues/104789)

## Description {#description}

Fluid standalone will add proper language syntax for booleans and `null`
with Fluid v4, which will be used in TYPO3 v13. Thus, user-defined variables
named `true`, `false` and `null` are no longer allowed.

## Impact {#impact}

Assigning variables with name `true`, `false` or `null` will throw
an exception in Fluid v4. In preparation of this change, Fluid v2.15 logs a
deprecation level error message if any of these variable names are used.

## Affected installations {#affected-installations}

Instances with Fluid templates using `true`, `false` or `null` as user-defined variable names.
This should rarely happen, as it would involve using `$view->assign('true', $someVar)`.

## Migration {#migration}

Template code using these variables should be adjusted to use different variable names.
In Fluid v4, the variables will contain their matching PHP counterparts.