diff --git a/man/shadowsocks-libev.8 b/man/shadowsocks-libev.8
index 5a6a47a4..2b448354 100644
--- a/man/shadowsocks-libev.8
+++ b/man/shadowsocks-libev.8
@@ -116,7 +116,7 @@ Not available in server nor manager mode.
 .B \-u
 Enable UDP relay.
 
-TPROXY is required in redir mode.
+TPROXY is required in redir mode. You may need root permission.
 .TP
 .B \-U
 Enable UDP relay and disable TCP relay.
diff --git a/man/ss-redir.1 b/man/ss-redir.1
index 5b85e0bd..a0d3bf89 100644
--- a/man/ss-redir.1
+++ b/man/ss-redir.1
@@ -95,7 +95,7 @@ Specify local address to bind.
 .B \-u
 Enable UDP relay.
 
-TPROXY is required in redir mode.
+TPROXY is required in redir mode. You may need root permission.
 .TP
 .B \-U
 Enable UDP relay and disable TCP relay.