diff --git a/doc/spec/dir-spec.txt b/doc/spec/dir-spec.txt
index a010836156..1f22290f5c 100644
--- a/doc/spec/dir-spec.txt
+++ b/doc/spec/dir-spec.txt
@@ -213,6 +213,7 @@ $Id$
 
   More formally:
 
+    NL = The ascii LF character (hex value 0x0a).
     Document ::= (Item | NL)+
     Item ::= KeywordLine Object*
     KeywordLine ::= Keyword NL | Keyword WS ArgumentChar+ NL