diff --git a/Doc/lib/libbase64.tex b/Doc/lib/libbase64.tex
index 0039c842501..d7eccbdb19c 100644
--- a/Doc/lib/libbase64.tex
+++ b/Doc/lib/libbase64.tex
@@ -21,7 +21,7 @@ three alphabets.  The legacy interface provides for encoding and
 decoding to and from file-like objects as well as strings, but only
 using the Base64 standard alphabet.
 
-The modern interface provides:
+The modern interface, which was introduced in Python 2.4, provides:
 
 \begin{funcdesc}{b64encode}{s\optional{, altchars}}
 Encode a string use Base64.