diff --git a/idn/punycode.go b/idn/punycode.go
index d71e6e9f..69c689cb 100644
--- a/idn/punycode.go
+++ b/idn/punycode.go
@@ -1,3 +1,4 @@
+// Package idn implements encoding from and to punycode as speficied by RFC 3492.
 package idn
 
 import (