---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/51115#article
headline: "51115: Twilsock: Invalid access token subject"
url: https://www.twilio.com/docs/api/errors/51115
inLanguage: en
dateModified: 2026-06-09T11:00:42.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 51115: Twilsock: Invalid access token subject

Log Level: ERROR

## Description

Twilsock could not accept the Access Token because the token `sub` claim is invalid. Use an Access Token with a valid subject that identifies the user for your client connection.

### Possible causes

* The Access Token is malformed and the `sub` claim cannot be parsed.
* The token was generated with an empty, missing, or invalid identity value.
* The token subject does not match the identity format expected by the Twilio SDK or service you are using.
* Your application is passing the wrong token to the client when establishing a Twilsock connection.
* The token was modified after it was generated, which made the subject invalid.

### Possible solutions

* Generate a new Access Token on your server and make sure it includes a valid identity for the user.
* Verify that your token generation code sets the user identity correctly before signing the token.
* Confirm that your client is using the current token returned by your server and not a stale or truncated token.
* Decode the token in your application to verify that the `sub` claim and related identity values are present and valid.
* If you rotate signing keys or credentials, make sure your application is not mixing tokens generated from different environments or projects.
* Review the Access Token format and identity requirements for the Twilio SDK product you are using.

#### Additional resources

* [Access Tokens](/docs/iam/access-tokens)
* [Identity and Access Management](/docs/iam)
* [Conversations documentation](/docs/conversations)