diff --git a/gluon/html.py b/gluon/html.py
index 362b8597..0909290c 100644
--- a/gluon/html.py
+++ b/gluon/html.py
@@ -32,6 +32,7 @@ regex_crlf = re.compile('\r|\n')
 
 join = ''.join
 
+# name2codepoint is incomplete respect to xhtml (and xml): 'apos' is missing.
 entitydefs = dict(map(lambda (k,v): (k, unichr(v).encode('utf-8')), name2codepoint.iteritems()))
 entitydefs.setdefault('apos', u"'")