merge headers, don't overwrite

diff --git a/requests/sessions.py b/requests/sessions.py
index 540089cc85cc4f472f698759bc7cb265132aca47..50b09f612de83e2eb1e524b8e58f8fccf69e939a 100644 (file)
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -67,6 +67,9 @@ class Session(object):
                         inst_attrs['cookies'], kwargs['cookies']
                     )
 
+                if kwargs.get('headers', None) and inst_attrs.get('headers', None):
+                    kwargs['headers'].update(inst_attrs['headers'])
+
                 return func(*args, **kwargs)
             return wrapper_func