From d2f647cee45fd05cc1977cc3faf4b095b5047b29 Mon Sep 17 00:00:00 2001
From: Ian Cordasco <graffatcolmingov@gmail.com>
Date: Fri, 14 Feb 2014 16:15:21 -0600
Subject: [PATCH] Do not set headers with None value

- Regardless of whether they are on the session or not
- Fixes #1920
---
 requests/sessions.py | 2 ++
 test_requests.py     | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/requests/sessions.py b/requests/sessions.py
index a023e4ec..c06fbcbe 100644
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -59,6 +59,8 @@ def merge_setting(request_setting, session_setting, dict_class=OrderedDict):
         if v is None:
             del merged_setting[k]
 
+    merged_setting = dict((k, v) for (k, v) in merged_setting.items() if v is not None)
+
     return merged_setting
 
 
diff --git a/test_requests.py b/test_requests.py
index 3d7cdaaf..998f17f3 100755
--- a/test_requests.py
+++ b/test_requests.py
@@ -211,6 +211,14 @@ class RequestsTestCase(unittest.TestCase):
         req_urls = [r.request.url for r in resp.history]
         assert urls == req_urls
 
+    def test_headers_on_session_with_None_are_not_sent(self):
+        """Do not send headers in Session.headers with None values."""
+        ses = requests.Session()
+        ses.headers['Accept-Encoding'] = None
+        req = requests.Request('GET', 'http://httpbin.org/get')
+        prep = ses.prepare_request(req)
+        assert 'Accept-Encoding' not in prep.headers
+
     def test_user_agent_transfers(self):
 
         heads = {