# 12101: Invalid Twilio Markup XML version

Log Level: ERROR

## Description

The version attribute of the Response root element is not valid.

### Possible causes

* an invalid value was provided for the "version" attribute of the [Response](/docs/voice/twiml#responding-to-twilio) root element.

### Possible solutions

* refer to the [versions](/docs/voice/twiml#responding-to-twilio) documentation for information on valid version values.