diff --git a/git_review/cmd.py b/git_review/cmd.py
index 19adfae2..f60bea71 100644
--- a/git_review/cmd.py
+++ b/git_review/cmd.py
@@ -171,7 +171,7 @@ def git_credentials(url):
     """Return credentials using git credential or None."""
     cmd = 'git', 'credential', 'fill'
     stdin = 'url=%s' % url
-    rc, out = run_command_status(*cmd, stdin=stdin.encode('utf-8'))
+    rc, out = run_command_status(*cmd, stdin=stdin)
     if rc:
         return None
     data = dict(line.split('=', 1) for line in out.splitlines())
diff --git a/git_review/tests/test_unit.py b/git_review/tests/test_unit.py
index 0854ebc7..9e201536 100644
--- a/git_review/tests/test_unit.py
+++ b/git_review/tests/test_unit.py
@@ -305,7 +305,7 @@ class GitReviewUnitTest(testtools.TestCase):
         # This gets encoded to utf8 which means the type passed down
         # is bytes.
         mock_run.assert_called_once_with('git', 'credential', 'fill',
-                                         stdin=b'url=%s' % url.encode('utf-8'))
+                                         stdin='url=%s' % url)
         calls = [mock.call(url), mock.call(url, auth=('user', 'pass'))]
         mock_get.assert_has_calls(calls)
 
@@ -323,7 +323,7 @@ class GitReviewUnitTest(testtools.TestCase):
         # This gets encoded to utf8 which means the type passed down
         # is bytes.
         mock_run.assert_called_once_with('git', 'credential', 'fill',
-                                         stdin=b'url=%s' % url.encode('utf-8'))
+                                         stdin='url=%s' % url)
         calls = [mock.call(url), mock.call(url, auth=('user', 'pass'))]
         mock_get.assert_has_calls(calls)
 
@@ -341,7 +341,7 @@ class GitReviewUnitTest(testtools.TestCase):
         # This gets encoded to utf8 which means the type passed down
         # is bytes.
         mock_run.assert_called_once_with('git', 'credential', 'fill',
-                                         stdin=b'url=%s' % url.encode('utf-8'))
+                                         stdin='url=%s' % url)
         mock_get.assert_called_once_with(url)
 
     @mock.patch('sys.argv', ['argv0', '--track', 'branch'])
diff --git a/test-requirements.txt b/test-requirements.txt
index 19da82ed..ad03fc16 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,5 +1,5 @@
 hacking>=2.0.0,<2.1.0
 mock
 fixtures>=0.3.14
-stestr>=2.2.0
+stestr>=2.2.0,<3.0.0
 testtools>=0.9.34