diff -r 764a758780b6 -r c007e5c54b16 mercurial/hgweb/server.py
--- a/mercurial/hgweb/server.py	Tue Jan 15 01:05:12 2013 +0100
+++ b/mercurial/hgweb/server.py	Tue Jan 15 01:05:12 2013 +0100
@@ -136,6 +136,8 @@
         self.length = None
         for chunk in self.server.application(env, self._start_response):
             self._write(chunk)
+        if not self.sent_headers:
+            self.send_headers()
 
     def send_headers(self):
         if not self.saved_status: