---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21228#article
headline: "21228: Invalid SIP Header. Illegal chars in header name"
url: https://www.twilio.com/docs/api/errors/21228
inLanguage: en
dateModified: 2025-12-18T21:40:49.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21228: Invalid SIP Header. Illegal chars in header name

Log Level: WARNING

## Description

The header you passed has characters not allowed in SIP.