diff --git a/python2/httplib2/__init__.py b/python2/httplib2/__init__.py
index 16fe452..158e967 100644
--- a/python2/httplib2/__init__.py
+++ b/python2/httplib2/__init__.py
@@ -518,7 +518,7 @@
                     self.challenge['cnonce'],
                     self.challenge['qop'], H(A2)
                     ))
-        headers['Authorization'] = 'Digest username="%s", realm="%s", nonce="%s", uri="%s", algorithm=%s, response=%s, qop=%s, nc=%08x, cnonce="%s"' % (
+        headers['authorization'] = 'Digest username="%s", realm="%s", nonce="%s", uri="%s", algorithm=%s, response=%s, qop=%s, nc=%08x, cnonce="%s"' % (
                 self.credentials[0],
                 self.challenge['realm'],
                 self.challenge['nonce'],
@@ -591,7 +591,7 @@
         cnonce = _cnonce()
         request_digest = "%s:%s:%s:%s:%s" % (method, request_uri, cnonce, self.challenge['snonce'], headers_val)
         request_digest  = hmac.new(self.key, request_digest, self.hashmod).hexdigest().lower()
-        headers['Authorization'] = 'HMACDigest username="%s", realm="%s", snonce="%s", cnonce="%s", uri="%s", created="%s", response="%s", headers="%s"' % (
+        headers['authorization'] = 'HMACDigest username="%s", realm="%s", snonce="%s", cnonce="%s", uri="%s", created="%s", response="%s", headers="%s"' % (
                 self.credentials[0],
                 self.challenge['realm'],
                 self.challenge['snonce'],
@@ -623,7 +623,7 @@
     def request(self, method, request_uri, headers, content):
         """Modify the request headers to add the appropriate
         Authorization header."""
-        headers['Authorization'] = 'WSSE profile="UsernameToken"'
+        headers['authorization'] = 'WSSE profile="UsernameToken"'
         iso_now = time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
         cnonce = _cnonce()
         password_digest = _wsse_username_token(cnonce, iso_now, self.credentials[1])
diff --git a/python2/httplib2test.py b/python2/httplib2test.py
index 9a9e792..1efcd3c 100755
--- a/python2/httplib2test.py
+++ b/python2/httplib2test.py
@@ -1463,11 +1463,11 @@
             'www-authenticate': 'Digest realm="myrealm", nonce="Ygk86AsKBAA=3516200d37f9a3230352fde99977bd6d472d4306", algorithm=MD5, qop="auth"'
         }
         content = ""
-        
+
         d = httplib2.DigestAuthentication(credentials, host, request_uri, headers, response, content, None)
         d.request("GET", request_uri, headers, content, cnonce="33033375ec278a46") 
-        our_request = "Authorization: %s" % headers['Authorization']
-        working_request = 'Authorization: Digest username="joe", realm="myrealm", nonce="Ygk86AsKBAA=3516200d37f9a3230352fde99977bd6d472d4306", uri="/projects/httplib2/test/digest/", algorithm=MD5, response="97ed129401f7cdc60e5db58a80f3ea8b", qop=auth, nc=00000001, cnonce="33033375ec278a46"'
+        our_request = "authorization: %s" % headers['authorization']
+        working_request = 'authorization: Digest username="joe", realm="myrealm", nonce="Ygk86AsKBAA=3516200d37f9a3230352fde99977bd6d472d4306", uri="/projects/httplib2/test/digest/", algorithm=MD5, response="97ed129401f7cdc60e5db58a80f3ea8b", qop=auth, nc=00000001, cnonce="33033375ec278a46"'
         self.assertEqual(our_request, working_request)
 
 
diff --git a/python3/httplib2/__init__.py b/python3/httplib2/__init__.py
index 4117e59..4f60a3a 100644
--- a/python3/httplib2/__init__.py
+++ b/python3/httplib2/__init__.py
@@ -501,7 +501,7 @@
                     self.challenge['cnonce'], 
                     self.challenge['qop'], H(A2)
                     )) 
-        headers['Authorization'] = 'Digest username="%s", realm="%s", nonce="%s", uri="%s", algorithm=%s, response=%s, qop=%s, nc=%08x, cnonce="%s"' % (
+        headers['authorization'] = 'Digest username="%s", realm="%s", nonce="%s", uri="%s", algorithm=%s, response=%s, qop=%s, nc=%08x, cnonce="%s"' % (
                 self.credentials[0], 
                 self.challenge['realm'],
                 self.challenge['nonce'],
@@ -574,7 +574,7 @@
         cnonce = _cnonce()
         request_digest = "%s:%s:%s:%s:%s" % (method, request_uri, cnonce, self.challenge['snonce'], headers_val)
         request_digest  = hmac.new(self.key, request_digest, self.hashmod).hexdigest().lower()
-        headers['Authorization'] = 'HMACDigest username="%s", realm="%s", snonce="%s", cnonce="%s", uri="%s", created="%s", response="%s", headers="%s"' % (
+        headers['authorization'] = 'HMACDigest username="%s", realm="%s", snonce="%s", cnonce="%s", uri="%s", created="%s", response="%s", headers="%s"' % (
                 self.credentials[0], 
                 self.challenge['realm'],
                 self.challenge['snonce'],
@@ -606,7 +606,7 @@
     def request(self, method, request_uri, headers, content):
         """Modify the request headers to add the appropriate
         Authorization header."""
-        headers['Authorization'] = 'WSSE profile="UsernameToken"'
+        headers['authorization'] = 'WSSE profile="UsernameToken"'
         iso_now = time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
         cnonce = _cnonce()
         password_digest = _wsse_username_token(cnonce, iso_now, self.credentials[1])
diff --git a/python3/httplib2test.py b/python3/httplib2test.py
index 40e087c..870275f 100755
--- a/python3/httplib2test.py
+++ b/python3/httplib2test.py
@@ -1416,11 +1416,11 @@
             'www-authenticate': 'Digest realm="myrealm", nonce="Ygk86AsKBAA=3516200d37f9a3230352fde99977bd6d472d4306", algorithm=MD5, qop="auth"'
         }
         content = b""
-        
+
         d = httplib2.DigestAuthentication(credentials, host, request_uri, headers, response, content, None)
         d.request("GET", request_uri, headers, content, cnonce="33033375ec278a46") 
-        our_request = "Authorization: %s" % headers['Authorization']
-        working_request = 'Authorization: Digest username="joe", realm="myrealm", nonce="Ygk86AsKBAA=3516200d37f9a3230352fde99977bd6d472d4306", uri="/projects/httplib2/test/digest/", algorithm=MD5, response="97ed129401f7cdc60e5db58a80f3ea8b", qop=auth, nc=00000001, cnonce="33033375ec278a46"'
+        our_request = "authorization: %s" % headers['authorization']
+        working_request = 'authorization: Digest username="joe", realm="myrealm", nonce="Ygk86AsKBAA=3516200d37f9a3230352fde99977bd6d472d4306", uri="/projects/httplib2/test/digest/", algorithm=MD5, response="97ed129401f7cdc60e5db58a80f3ea8b", qop=auth, nc=00000001, cnonce="33033375ec278a46"'
         self.assertEqual(our_request, working_request)