diff -r 66d0f6ef2a7f Lib/test/test_urllib2net.py
--- a/Lib/test/test_urllib2net.py	Thu Feb 28 18:03:16 2013 +0200
+++ b/Lib/test/test_urllib2net.py	Wed Mar 20 11:00:54 2013 -0400
@@ -177,6 +177,21 @@
             opener.open(request)
             self.assertEqual(request.get_header('User-agent'),'Test-Agent')
 
+    def test_headers_case_sensitivity(self):
+        url = "http://www.example.com"
+        with support.transient_internet(url):
+            opener = urllib.request.build_opener()
+            request = urllib.request.Request(url)
+            headers = [("Content-Type", "text/plain"), ]
+            opener.addheaders = headers
+            opener.open(request)
+            self.assertTrue(request.has_header('Content-type'))
+            self.assertTrue(request.has_header('Content-Type'))
+            self.assertTrue(request.has_header('content-type'))
+            self.assertEqual(request.get_header('Content-type'), 'text/plain')
+            self.assertEqual(request.get_header('Content-Type'), 'text/plain')
+            self.assertEqual(request.get_header('content-type'), 'text/plain')
+
     def test_sites_no_connection_close(self):
         # Some sites do not send Connection: close header.
         # Verify that those work properly. (#issue12576)