=== trac/web/api.py
==================================================================
--- trac/web/api.py	(revision 6806)
+++ trac/web/api.py	(local)
@@ -191,7 +191,7 @@
 
     def send_header(self, name, value):
         """Send the response header with the specified name and value."""
-        self._outheaders.append((name, value))
+        self._outheaders.append((name, str(value)))
 
     def _send_cookie_headers(self):
         for name in self.outcookie.keys():