diff --git a/scrapy/responsetypes.py b/scrapy/responsetypes.py
index b519c56d3..4880cc7b9 100644
--- a/scrapy/responsetypes.py
+++ b/scrapy/responsetypes.py
@@ -1,9 +1,8 @@
 """
 This module implements a class which returns the appropriate Response class
 based on different criteria.
-
 """
-
+from __future__ import absolute_import
 from mimetypes import MimeTypes
 from pkgutil import get_data
 from io import StringIO
@@ -13,6 +12,7 @@ from scrapy.http import Response
 from scrapy.utils.misc import load_object
 from scrapy.utils.python import isbinarytext, to_bytes, to_native_str
 
+
 class ResponseTypes(object):
 
     CLASSES = {
@@ -69,11 +69,13 @@ class ResponseTypes(object):
         """Return the most appropriate Response class by looking at the HTTP
         headers"""
         cls = Response
-        if 'Content-Type' in headers:
-            cls = self.from_content_type(headers['Content-type'], \
-                headers.get('Content-Encoding'))
-        if cls is Response and 'Content-Disposition' in headers:
-            cls = self.from_content_disposition(headers['Content-Disposition'])
+        if b'Content-Type' in headers:
+            cls = self.from_content_type(
+                content_type=headers[b'Content-type'],
+                content_encoding=headers.get(b'Content-Encoding')
+            )
+        if cls is Response and b'Content-Disposition' in headers:
+            cls = self.from_content_disposition(headers[b'Content-Disposition'])
         return cls
 
     def from_filename(self, filename):
@@ -101,7 +103,8 @@ class ResponseTypes(object):
             return self.from_mimetype('text')
 
     def from_args(self, headers=None, url=None, filename=None, body=None):
-        """Guess the most appropriate Response class based on the given arguments"""
+        """Guess the most appropriate Response class based on
+        the given arguments."""
         cls = Response
         if headers is not None:
             cls = self.from_headers(headers)
diff --git a/tests/py3-ignores.txt b/tests/py3-ignores.txt
index 47abd8004..c51bc5981 100644
--- a/tests/py3-ignores.txt
+++ b/tests/py3-ignores.txt
@@ -30,7 +30,6 @@ tests/test_mail.py
 tests/test_pipeline_files.py
 tests/test_pipeline_images.py
 tests/test_proxy_connect.py
-
 tests/test_selector_csstranslator.py
 tests/test_selector_lxmldocument.py
 tests/test_selector.py