@@ -15,6 +15,7 @@ import base64

 from . import Config

 from logging import debug

 from .Utils import encode_to_s3, time_to_epoch, deunicodise, decode_from_s3

+from .SortedDict import SortedDict

 import datetime

 try:

@@ -227,10 +228,10 @@ def sign_request_v4(method='GET', host='', canonical_uri='/', params=None,

     signature = decode_from_s3(hmac.new(signing_key, encode_to_s3(string_to_sign), sha256).hexdigest())

     authorization_header = algorithm + ' ' + 'Credential=' + access_key + '/' + credential_scope + ',' +  'SignedHeaders=' + signed_headers + ',' + 'Signature=' + signature

-    new_headers = dict(list(cur_headers.items()) + list({'x-amz-date':amzdate,

-                                          'Authorization':authorization_header,

-                                          'x-amz-content-sha256': payload_hash

-                                         }.items()))

+    new_headers = SortedDict(cur_headers.items())

+    new_headers.update({'x-amz-date':amzdate,

+                       'Authorization':authorization_header,

+                       'x-amz-content-sha256': payload_hash})

     debug("signature-v4 headers: %s" % new_headers)

     return new_headers

 __all__.append("sign_request_v4")