diff --git a/tests/unit/cryptstream/test_cryptblob.py b/tests/unit/cryptstream/test_cryptblob.py
index 032084842..6a6005ae0 100644
--- a/tests/unit/cryptstream/test_cryptblob.py
+++ b/tests/unit/cryptstream/test_cryptblob.py
@@ -8,14 +8,14 @@ from tests.mocks import mock_conf_settings
 from cryptography.hazmat.primitives.ciphers.algorithms import AES
 import random
 import string
-import StringIO
+from six import BytesIO
 import os
 
-AES_BLOCK_SIZE_BYTES = AES.block_size / 8
+AES_BLOCK_SIZE_BYTES = int(AES.block_size / 8)
 
 class MocBlob(object):
     def __init__(self):
-        self.data = ''
+        self.data = b''
 
     def read(self, write_func):
         data = self.data
@@ -23,9 +23,11 @@ class MocBlob(object):
         return defer.succeed(True)
 
     def open_for_reading(self):
-        return StringIO.StringIO(self.data)
+        return BytesIO(self.data)
 
     def write(self, data):
+        if not isinstance(data, bytes):
+            data = data.encode()
         self.data += data
 
     def close(self):
@@ -33,7 +35,7 @@ class MocBlob(object):
 
 
 def random_string(length):
-    return ''.join(random.choice(string.lowercase) for i in range(length))
+    return ''.join(random.choice(string.ascii_lowercase) for i in range(length))
 
 
 class TestCryptBlob(unittest.TestCase):
@@ -50,20 +52,20 @@ class TestCryptBlob(unittest.TestCase):
         iv = os.urandom(AES_BLOCK_SIZE_BYTES)
         maker = CryptBlob.CryptStreamBlobMaker(key, iv, blob_num, blob)
         write_size = size_of_data
-        string_to_encrypt = random_string(size_of_data)
+        string_to_encrypt = random_string(size_of_data).encode()
 
         # encrypt string
         done, num_bytes = maker.write(string_to_encrypt)
         yield maker.close()
         self.assertEqual(size_of_data, num_bytes)
-        expected_encrypted_blob_size = ((size_of_data / AES_BLOCK_SIZE_BYTES) + 1) * AES_BLOCK_SIZE_BYTES
+        expected_encrypted_blob_size = int((size_of_data / AES_BLOCK_SIZE_BYTES) + 1) * AES_BLOCK_SIZE_BYTES
         self.assertEqual(expected_encrypted_blob_size, len(blob.data))
 
         if size_of_data < MAX_BLOB_SIZE-1:
             self.assertFalse(done)
         else:
             self.assertTrue(done)
-        self.data_buf = ''
+        self.data_buf = b''
 
         def write_func(data):
             self.data_buf += data