diff --git a/PyPDF2/filters.py b/PyPDF2/filters.py
index 270ba0d12..3bd773bfd 100644
--- a/PyPDF2/filters.py
+++ b/PyPDF2/filters.py
@@ -45,9 +45,7 @@
 
 if version_info < ( 3, 0 ):
     from cStringIO import StringIO as BytesIO
-    bytearray = buffer
-else:
-    from io import StringIO
+    bytearray = buffer  # noqa: F821
 
 import struct