diff --git a/doc/url-params.md b/doc/url-params.md
index 5912d78..58419f5 100644
--- a/doc/url-params.md
+++ b/doc/url-params.md
@@ -3,7 +3,8 @@
 gamja settings can be overridden using URL query parameters:
 
 - `server`: path or URL to the WebSocket server
-- `nick`: nickname
+- `nick`: nickname (if the character `*` appears in the string, it will be
+  replaced with a randomly generated value)
 - `channels`: comma-separated list of channels to join (`#` needs to be escaped)
 - `open`: [IRC URL] to open
 - `debug`: if set to 1, debug mode is enabled