lib/python/web_support.py

@@ -674,6 +674,7 @@ class BinaryResult(Result):
         self.contents = contents
         self.status = status
         self.headers['Content-Type'] = mimetype
+        self.headers['Content-Length'] = str(len(self.contents))
 
     def flatten(self, write):
         """Invokes write for the response header and the binary data."""