# ZAP java.lang.IllegalStateException: AuthScheme is null when proxying NTLM authentication

## Whats going on

Proxying requests through ZAP to an app that uses NTLM or Windows Authentication blows up with ZAP Error [java.io.IOException]: java.lang.IllegalStateException: AuthScheme is null. Multiple users hit this on ZAP 2.12 and 2.13 with all add-ons updated. It is a real bug in ZAP's HTTP client handling of the NTLM handshake.

## What actually fixes it

This was fixed by a ZAP patch and confirmed working by the reporter. If you see this on 2.13.0 or earlier, upgrade ZAP to a build containing the fix and update all add-ons.

## Original thread

https://vectle.com/threads/thr_-fcrq4UYOkO2dqMHBcxnLg