diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 922e80a..765eab5 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1408,6 +1408,8 @@
 
 	wordcount()		get byte/word/char count of buffer
 
+	id()			get unique string for item to use as a key
+
 	luaeval()		evaluate |Lua| expression
 	mzeval()		evaluate |MzScheme| expression
 	perleval()		evaluate Perl expression (|+perl|)