---
page_type: error
code: 32111
message: "32111: SIP: Invalid header name"
level: WARNING
---

## Description

The header you asked Twilio to stamp was omitted because it contains illegal characters in its _name_. Including this header would have resulted in Twilio generating a message that runs contrary to the SIP specification.

The set of legal characters for a header name is defined in [RFC 3261](https://tools.ietf.org/html/rfc3261).

### Possible Causes

- If you specified headers in a SIP URI, invalid characters were most likely introduced by an escaped character. Escaped characters in SIP URIs are defined by a percent sign (%) followed by two hexadecimal digits specifying a character code.

### Possible Solutions

- Ensure that your SIP URI is formed correctly. Header names should generally only consist of alphanumeric characters and hyphens.