diff --git a/rawmsg.go b/rawmsg.go
index a4903b96..b3d63148 100644
--- a/rawmsg.go
+++ b/rawmsg.go
@@ -24,6 +24,7 @@ func (h *RR_Header) RawSetRdlength(buf []byte, off int) bool {
 	return true
 }
 
+// RawSetId sets the message ID in buf.
 func RawSetId(buf []byte, off int, id uint16) bool {
         buf[off], buf[off+1] = packUint16(id)
         return true