diff --git a/mayan/apps/common/compressed_files.py b/mayan/apps/common/compressed_files.py
index 1e7bfb3914..646d0b5724 100644
--- a/mayan/apps/common/compressed_files.py
+++ b/mayan/apps/common/compressed_files.py
@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+from io import BytesIO
 import zipfile
 
 try:
@@ -8,11 +9,6 @@ try:
 except:
     COMPRESSION = zipfile.ZIP_STORED
 
-try:
-    from cStringIO import StringIO
-except ImportError:
-    from StringIO import StringIO
-
 from django.core.files.uploadedfile import SimpleUploadedFile
 
 
@@ -35,7 +31,7 @@ class CompressedFile(object):
             self._create()
 
     def _create(self):
-        self.descriptor = StringIO()
+        self.descriptor = BytesIO()
         self.zf = zipfile.ZipFile(self.descriptor, mode='w')
 
     def _open(self, file_input):
diff --git a/mayan/apps/converter/backends/python.py b/mayan/apps/converter/backends/python.py
index dfeaaeeb77..706c8a744d 100644
--- a/mayan/apps/converter/backends/python.py
+++ b/mayan/apps/converter/backends/python.py
@@ -4,11 +4,6 @@ import io
 import logging
 import os
 
-try:
-    from cStringIO import StringIO
-except ImportError:
-    from StringIO import StringIO
-
 from PIL import Image
 import PyPDF2
 import sh
@@ -66,7 +61,7 @@ logger = logging.getLogger(__name__)
 
 class IteratorIO(object):
     def __init__(self, iterator):
-        self.file_buffer = StringIO()
+        self.file_buffer = io.BytesIO()
 
         for chunk in iterator:
             self.file_buffer.write(chunk)
diff --git a/mayan/apps/converter/classes.py b/mayan/apps/converter/classes.py
index 1fa4002a17..7b7b6b3fd9 100644
--- a/mayan/apps/converter/classes.py
+++ b/mayan/apps/converter/classes.py
@@ -1,18 +1,15 @@
 from __future__ import unicode_literals
 
 import base64
+from io import BytesIO
 import logging
 import os
 
-try:
-    from cStringIO import StringIO
-except ImportError:
-    from StringIO import StringIO
-
 from PIL import Image, ImageFilter
 import sh
 import yaml
 
+from django.utils.six import text_type
 from django.utils.translation import string_concat, ugettext_lazy as _
 
 from common.settings import setting_temporary_directory
@@ -193,7 +190,7 @@ class ConverterBase(object):
         if not self.image:
             self.seek(0)
 
-        image_buffer = StringIO()
+        image_buffer = BytesIO()
         new_mode = self.image.mode
 
         if output_format.upper() == 'JPEG':
@@ -296,7 +293,7 @@ class BaseTransformation(object):
             self.kwargs[argument_name] = kwargs.get(argument_name)
 
     def cache_hash(self):
-        result = unicode.__hash__(self.name)
+        result = text_type.__hash__(self.name)
         for index, (key, value) in enumerate(self.kwargs.items()):
             result ^= hash((key, index)) ^ hash((value, index))