diff --git a/docs/user-guide/configuration.md b/docs/user-guide/configuration.md
index 64de6c2..82e3b29 100644
--- a/docs/user-guide/configuration.md
+++ b/docs/user-guide/configuration.md
@@ -106,6 +106,7 @@ httpproxy.inbound.length               | Inbound tunnels length if keys is set.
 httpproxy.inbound.quantity             | Inbound tunnels quantity if keys is set. 5 by default  
 httpproxy.outbound.length              | Outbound tunnels length if keys is set. 3 by default  
 httpproxy.outbound.quantity            | Outbound tunnels quantity if keys is set. 5 by default    
+httpproxy.outproxy                     | HTTP proxy upstream out proxy url (like http://false.i2p)  
 
 ### Socks proxy