ErrorDocument 502 external + mod_proxy

HI ALL,
I have maschine where mod_proxy is used to proxypass requests to tomcat
ProxyPass / http://tomcat:8080/
ProxyPassReverse / http://tomcat:8080/

Somtimes tomcat goes out and error 502 appear:

"502 Proxy Error
The Proxy Server received an invalid response
from an upstream server.
Reason: Error reading from remote server."

Here is problem - I was asked to put ErrorDocument 502 page instead this
message,
so i created virtual called "errors" end put directive to previous one:
"ErrorDocument 502 http://errors/errorpage.html"
And that is not working instead of page - text shows:

"Proxy Error
The document has moved here."

where "here" is link to http://errors/errorpage.html

Do anyone has idea how to make it to automatically move - without mod_proxy
it works fine.

Thanks for any help.


--
Pozdr.
JK.