diff --git a/Lib/quopri.py b/Lib/quopri.py
index 55608d12061..47ef7512c4b 100755
--- a/Lib/quopri.py
+++ b/Lib/quopri.py
@@ -1,4 +1,4 @@
-# Conversions to/from quoted-printable transport encoding as per RFC-XXXX
+# Conversions to/from quoted-printable transport encoding as per RFC-1521
 # (Dec 1991 version).
 
 ESCAPE = '='