diff --git a/pelican/settings.py b/pelican/settings.py
index c04cc5d0..ba28905a 100644
--- a/pelican/settings.py
+++ b/pelican/settings.py
@@ -99,6 +99,7 @@ DEFAULT_CONFIG = {
     'DEFAULT_DATE_FORMAT': '%a %d %B %Y',
     'DATE_FORMATS': {},
     'MD_EXTENSIONS': ['codehilite(css_class=highlight)', 'extra'],
+    'MD_OUTPUT_FORMAT': 'xhtml1',
     'JINJA_EXTENSIONS': [],
     'JINJA_FILTERS': {},
     'LOG_FILTER': [],