diff --git a/stripe/api_resources/source.py b/stripe/api_resources/source.py
index 074062202..db910d796 100644
--- a/stripe/api_resources/source.py
+++ b/stripe/api_resources/source.py
@@ -36,7 +36,8 @@ def detach(self, idempotency_key=None, **params):
             )
 
     def source_transactions(self, **params):
-        """source_transactions is deprecated, use Source.list_source_transactions instead."""
+        """source_transactions is deprecated, use Source.list_source_transactions instead.
+        """
         return self.request(
             "get", self.instance_url() + "/source_transactions", params
         )
diff --git a/stripe/api_resources/subscription_item.py b/stripe/api_resources/subscription_item.py
index e601b8523..748d39c13 100644
--- a/stripe/api_resources/subscription_item.py
+++ b/stripe/api_resources/subscription_item.py
@@ -22,7 +22,8 @@ class SubscriptionItem(
     OBJECT_NAME = "subscription_item"
 
     def usage_record_summaries(self, **params):
-        """usage_record_summaries is deprecated, use SubscriptionItem.list_usage_record_summaries instead."""
+        """usage_record_summaries is deprecated, use SubscriptionItem.list_usage_record_summaries instead.
+        """
         return self.request(
             "get", self.instance_url() + "/usage_record_summaries", params
         )
diff --git a/stripe/oauth_error.py b/stripe/oauth_error.py
index 35f658700..b755b05cf 100644
--- a/stripe/oauth_error.py
+++ b/stripe/oauth_error.py
@@ -22,10 +22,8 @@ def construct_error_object(self):
         if self.json_body is None:
             return None
 
-        return (
-            stripe.api_resources.error_object.OAuthErrorObject.construct_from(
-                self.json_body, stripe.api_key
-            )
+        return stripe.api_resources.error_object.OAuthErrorObject.construct_from(
+            self.json_body, stripe.api_key
         )
 
 
diff --git a/tests/test_integration.py b/tests/test_integration.py
index fe3b64721..fe8c1a679 100644
--- a/tests/test_integration.py
+++ b/tests/test_integration.py
@@ -134,10 +134,8 @@ def do_GET(self):
 
         self.setup_mock_server(MockServerRequestHandler)
 
-        stripe.default_http_client = (
-            stripe.http_client.new_default_http_client(
-                proxy="http://localhost:%s" % self.mock_server_port
-            )
+        stripe.default_http_client = stripe.http_client.new_default_http_client(
+            proxy="http://localhost:%s" % self.mock_server_port
         )
         stripe.Balance.retrieve()
         assert MockServerRequestHandler.num_requests == 1
diff --git a/tox.ini b/tox.ini
index bd1f21fa0..722771e21 100644
--- a/tox.ini
+++ b/tox.ini
@@ -37,7 +37,7 @@ passenv = LDFLAGS CFLAGS
 [testenv:fmt]
 description = run code formatting using black
 basepython = python3.9
-deps = black==20.8b1
+deps = black==19.3b0
 commands = black . {posargs}
 skip_install = true