diff --git a/README.rst b/README.rst
index aeb971a4d..ff598c4e0 100644
--- a/README.rst
+++ b/README.rst
@@ -45,7 +45,7 @@ To use Ray's actor model:
     ray.init()
 
     @ray.remote
-    class Counter():
+    class Counter(object):
         def __init__(self):
             self.n = 0
 
diff --git a/ci/performance_tests/test_performance.py b/ci/performance_tests/test_performance.py
index 19a593583..c020343f1 100644
--- a/ci/performance_tests/test_performance.py
+++ b/ci/performance_tests/test_performance.py
@@ -119,7 +119,7 @@ def no_op(*values):
 
 
 @ray.remote
-class Actor():
+class Actor(object):
     def ping(self, *values):
         pass
 
diff --git a/doc/examples/doc_code/tf_example.py b/doc/examples/doc_code/tf_example.py
index 505bc543b..01a7f5d4c 100644
--- a/doc/examples/doc_code/tf_example.py
+++ b/doc/examples/doc_code/tf_example.py
@@ -48,7 +48,7 @@ def random_one_hot_labels(shape):
 # Use GPU wth
 # @ray.remote(num_gpus=1)
 @ray.remote
-class Network():
+class Network(object):
     def __init__(self):
         self.model = create_keras_model()
         self.dataset = np.random.random((1000, 32))
diff --git a/doc/examples/doc_code/torch_example.py b/doc/examples/doc_code/torch_example.py
index b89f6b5ae..77f2a0ae6 100644
--- a/doc/examples/doc_code/torch_example.py
+++ b/doc/examples/doc_code/torch_example.py
@@ -113,7 +113,7 @@ def dataset_creators(use_cuda):
 import torch.optim as optim
 
 
-class Network():
+class Network(object):
     def __init__(self, lr=0.01, momentum=0.5):
         use_cuda = torch.cuda.is_available()
         self.device = device = torch.device("cuda" if use_cuda else "cpu")
diff --git a/doc/examples/plot_pong_example.py b/doc/examples/plot_pong_example.py
index 9b0ef73dd..4c2b381de 100644
--- a/doc/examples/plot_pong_example.py
+++ b/doc/examples/plot_pong_example.py
@@ -156,7 +156,7 @@ def rollout(model, env):
 # given an input, which in our case is an observation.
 
 
-class Model():
+class Model(object):
     """This class holds the neural network weights."""
 
     def __init__(self):
diff --git a/doc/source/index.rst b/doc/source/index.rst
index 21d0b695e..5583ecc14 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -52,7 +52,7 @@ To use Ray's actor model:
     ray.init()
 
     @ray.remote
-    class Counter():
+    class Counter(object):
         def __init__(self):
             self.n = 0
 
diff --git a/python/ray/autoscaler/autoscaler.py b/python/ray/autoscaler/autoscaler.py
index f6b389134..61ef92fc8 100644
--- a/python/ray/autoscaler/autoscaler.py
+++ b/python/ray/autoscaler/autoscaler.py
@@ -354,7 +354,7 @@ class NodeLauncher(threading.Thread):
         logger.info(prefix + " {}".format(statement))
 
 
-class ConcurrentCounter():
+class ConcurrentCounter(object):
     def __init__(self):
         self._value = 0
         self._lock = threading.Lock()
diff --git a/python/ray/autoscaler/log_timer.py b/python/ray/autoscaler/log_timer.py
index 935f46b61..7506257d5 100644
--- a/python/ray/autoscaler/log_timer.py
+++ b/python/ray/autoscaler/log_timer.py
@@ -8,7 +8,7 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-class LogTimer():
+class LogTimer(object):
     def __init__(self, message):
         self._message = message
 
diff --git a/python/ray/experimental/serve/tests/test_metric.py b/python/ray/experimental/serve/tests/test_metric.py
index 84c5f7f3d..d60cb20f5 100644
--- a/python/ray/experimental/serve/tests/test_metric.py
+++ b/python/ray/experimental/serve/tests/test_metric.py
@@ -9,7 +9,7 @@ from ray.experimental.serve.metric import MetricMonitor
 @pytest.fixture(scope="session")
 def start_target_actor(ray_instance):
     @ray.remote
-    class Target():
+    class Target(object):
         def __init__(self):
             self.counter_value = 0
 
diff --git a/python/ray/tune/log_sync.py b/python/ray/tune/log_sync.py
index a2769af87..8d8433dfc 100644
--- a/python/ray/tune/log_sync.py
+++ b/python/ray/tune/log_sync.py
@@ -41,7 +41,7 @@ def log_sync_template():
             ).format(ssh_key=quote(ssh_key))
 
 
-class NodeSyncMixin():
+class NodeSyncMixin(object):
     """Mixin for syncing files to/from a remote dir to a local dir."""
 
     def __init__(self):
diff --git a/python/ray/tune/schedulers/hyperband.py b/python/ray/tune/schedulers/hyperband.py
index 064ae09aa..2ed6ecfdf 100644
--- a/python/ray/tune/schedulers/hyperband.py
+++ b/python/ray/tune/schedulers/hyperband.py
@@ -294,7 +294,7 @@ class HyperBandScheduler(FIFOScheduler):
         trial_runner.trial_executor.unpause_trial(trial)
 
 
-class Bracket():
+class Bracket(object):
     """Logical object for tracking Hyperband bracket progress. Keeps track
     of proper parameters as designated by HyperBand.
 
diff --git a/python/ray/tune/tests/test_commands.py b/python/ray/tune/tests/test_commands.py
index f640260be..8234ffd79 100644
--- a/python/ray/tune/tests/test_commands.py
+++ b/python/ray/tune/tests/test_commands.py
@@ -20,7 +20,7 @@ from ray.tune import commands
 from ray.tune.result import CONFIG_PREFIX
 
 
-class Capturing():
+class Capturing(object):
     def __enter__(self):
         self._stdout = sys.stdout
         sys.stdout = self._stringio = StringIO()