diff --git a/.travis.yml b/.travis.yml
index ce6426a56..c7e76728d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -47,7 +47,7 @@ install:
 
 script:
   - if [[ $TRAVIS_PYTHON_VERSION == '2.7' ]]; then make lint; fi
-  - if [[ $TRAVIS_PYTHON_VERSION == '3.7' ]]; then make fmtcheck; fi
+  - if [[ $TRAVIS_PYTHON_VERSION == '3.8' ]]; then make fmtcheck; fi
   - make ci
 
 after_success: make coveralls
diff --git a/tests/api_resources/test_credit_note.py b/tests/api_resources/test_credit_note.py
index f014b3793..10ffc7b8b 100644
--- a/tests/api_resources/test_credit_note.py
+++ b/tests/api_resources/test_credit_note.py
@@ -45,7 +45,7 @@ def test_is_modifiable(self, request_mock):
         assert isinstance(resource, stripe.CreditNote)
 
     def test_can_preview(self, request_mock):
-        resource = stripe.CreditNote.preview(invoice="in_123", amount=500,)
+        resource = stripe.CreditNote.preview(invoice="in_123", amount=500)
         request_mock.assert_requested("get", "/v1/credit_notes/preview")
         assert isinstance(resource, stripe.CreditNote)
 
diff --git a/tox.ini b/tox.ini
index 8aade7005..1abb46510 100644
--- a/tox.ini
+++ b/tox.ini
@@ -28,7 +28,7 @@ passenv = LDFLAGS CFLAGS
 [testenv:fmt]
 description = run code formatting using black
 basepython = python3.8
-deps = black
+deps = black==19.3b0
 commands = black . {posargs}
 skip_install = true