@@ -1281,7 +1281,7 @@ class S3(object):

         debug("MD5 sums: computed=%s, received=%s" % (md5_computed, response["headers"]["etag"]))

         ## when using KMS encryption, MD5 etag value will not match

-        if (response["headers"]["etag"].strip('"\'') != md5_hash.hexdigest()) and response["headers"]["x-amz-server-side-encryption"] != 'aws:kms':

+        if (response["headers"]["etag"].strip('"\'') != md5_hash.hexdigest()) and response["headers"].get("x-amz-server-side-encryption") != 'aws:kms':

             warning("MD5 Sums don't match!")

             if retries:

                 warning("Retrying upload of %s" % (filename))

@@ -1480,9 +1480,8 @@ class S3(object):

             warning("Reported size (%s) does not match received size (%s)" % (

                 start_position + long(response["headers"]["content-length"]), response["size"]))

         debug("ReceiveFile: Computed MD5 = %s" % response.get("md5"))

-        debug("sse headers : %s" % response["headers"]["x-amz-server-side-encryption"])

         # avoid ETags from multipart uploads that aren't the real md5

-        if ('-' not in md5_from_s3 and not response["md5match"]) and (response["headers"]["x-amz-server-side-encryption"] != 'aws:kms'):

+        if ('-' not in md5_from_s3 and not response["md5match"]) and (response["headers"].get("x-amz-server-side-encryption") != 'aws:kms'):

             warning("MD5 signatures do not match: computed=%s, received=%s" % (

                 response.get("md5"), md5_from_s3))

         return response