How to combine proxy and basic auth in Apache - apache

Question

How do you combine basic auth with a reverse proxy in Apache?
I have an Apache site currently configured to use basic auth with an htpasswd file using this config:
<VirtualHost *:80>
# Requires: a2enmod proxy_http
ProxyPass / http://127.0.0.1:8010/
<Location />
AuthType Basic
AuthName "Sensitive"
AuthUserFile /usr/local/myproject/htpasswd
Require valid-user
</Location>
</VirtualHost>
Apache is acting as a wrapper around a Buildbot server being served on port :8010. However, this app has been upgraded so it now requires the use of websockets. The suggested Apache configuration is:
<VirtualHost *:80>
<Location /ws>
ProxyPass ws://127.0.0.1:8010/ws
ProxyPassReverse ws://127.0.0.1:8010/ws
</Location>
ProxyPass /ws !
ProxyPass / http://127.0.0.1:8010/
ProxyPassReverse / http://127.0.0.1:8010/
</VirtualHost>
However, this doesn't use any authentication. I tried re-adding my <Location /> section from the previous config, so I now have:
<VirtualHost *:80>
<Location />
AuthType Basic
AuthName "Sensitive"
AuthUserFile /usr/local/myproject/htpasswd
Require valid-user
</Location>
<Location /ws>
ProxyPass ws://127.0.0.1:8010/ws
ProxyPassReverse ws://127.0.0.1:8010/ws
</Location>
ProxyPass /ws !
ProxyPass / http://127.0.0.1:8010/
ProxyPassReverse / http://127.0.0.1:8010/
</VirtualHost>
and although Apache now correctly prompts for my username+password, the Buildbot still isn't given authenticated username and still renders for an anonymous user.
How do I fix this config to pass the username (I believe the REMOTE_USER header) through to the web app behind the reverse proxy?