diff --git a/test/probe/brain.py b/test/probe/brain.py
index 6b94a3122b..e8eb8ca547 100644
--- a/test/probe/brain.py
+++ b/test/probe/brain.py
@@ -14,13 +14,13 @@
 from __future__ import print_function
 import functools
 import sys
+from io import BytesIO
 import itertools
 import uuid
 from optparse import OptionParser
 import random
 
 import six
-from six import StringIO
 from six.moves.urllib.parse import urlparse, parse_qs, quote
 
 from swift.common.manager import Manager
@@ -233,7 +233,7 @@ def translate_client_exception(m):
             return m(*args, **kwargs)
         except UnexpectedResponse as err:
             raise ClientException(
-                err.message,
+                err.args[0],
                 http_scheme=err.resp.environ['wsgi.url_scheme'],
                 http_host=err.resp.environ['SERVER_NAME'],
                 http_port=err.resp.environ['SERVER_PORT'],
@@ -274,7 +274,7 @@ class InternalBrainClient(object):
     @translate_client_exception
     def put_object(self, container_name, object_name, headers, contents,
                    query_string=None):
-        return self.swift.upload_object(StringIO(contents), self.account,
+        return self.swift.upload_object(BytesIO(contents), self.account,
                                         container_name, object_name,
                                         headers=headers,
                                         params=self.parse_qs(query_string))
@@ -294,7 +294,7 @@ class InternalBrainClient(object):
         status, headers, resp_iter = self.swift.get_object(
             self.account, container_name, object_name,
             params=self.parse_qs(query_string))
-        return headers, ''.join(resp_iter)
+        return headers, b''.join(resp_iter)
 
 
 @six.add_metaclass(meta_command)
diff --git a/test/probe/test_container_merge_policy_index.py b/test/probe/test_container_merge_policy_index.py
index f4a499d09d..665f621e97 100644
--- a/test/probe/test_container_merge_policy_index.py
+++ b/test/probe/test_container_merge_policy_index.py
@@ -358,9 +358,10 @@ class TestContainerMergePolicyIndex(ReplProbeTest):
                                         for i in range(20)))
 
         # and regular upload should work now too
-        self.brain.client.put_object(self.container_name, self.object_name, {},
-                                     utils.json.dumps(manifest_data),
-                                     query_string='multipart-manifest=put')
+        self.brain.client.put_object(
+            self.container_name, self.object_name, {},
+            utils.json.dumps(manifest_data).encode('ascii'),
+            query_string='multipart-manifest=put')
         metadata = self.brain.client.head_object(self.container_name,
                                                  self.object_name)
         self.assertEqual(int(metadata['content-length']),
@@ -392,7 +393,7 @@ class TestContainerMergePolicyIndex(ReplProbeTest):
                 'X-Symlink-Target': '%s/%s' % (
                     self.container_name, target_name),
                 'Content-Type': 'application/symlink',
-            }, '')
+            }, b'')
 
         # at this point we have a broken symlink (the container_info has the
         # proxy looking for the target in the wrong policy)