Fix a bug in the header generation

[fwx] / src / fwx / __init__.py

diff --git a/src/fwx/__init__.py b/src/fwx/__init__.py
index d26083b..6ee7541 100644 (file)
--- a/src/fwx/__init__.py
+++ b/src/fwx/__init__.py
@@ -158,7 +158,7 @@ class Response(_Response):
             'Content-Type': self.content_type,
         }
 
-        for key, value in builtin_headers:
+        for key, value in builtin_headers.items():
             if key in result:
                 raise Exception('Header "{}" defined twice'.format(key))
             else: