diff --git a/borgmatic/config/environment.py b/borgmatic/config/environment.py
index f79dfc9..3a58566 100644
--- a/borgmatic/config/environment.py
+++ b/borgmatic/config/environment.py
@@ -1,7 +1,9 @@
 import os
 import re
 
-_VARIABLE_PATTERN = re.compile(r'(?P<escape>\\)?(?P<variable>\$\{(?P<name>[A-Za-z0-9_]+)((:?-)(?P<default>[^}]+))?\})')
+_VARIABLE_PATTERN = re.compile(
+    r'(?P<escape>\\)?(?P<variable>\$\{(?P<name>[A-Za-z0-9_]+)((:?-)(?P<default>[^}]+))?\})'
+)
 
 
 def _resolve_string(matcher):
diff --git a/tests/unit/config/test_environment.py b/tests/unit/config/test_environment.py
index 6f5d1df..b7b56dd 100644
--- a/tests/unit/config/test_environment.py
+++ b/tests/unit/config/test_environment.py
@@ -16,6 +16,7 @@ def test_env_braces(monkeypatch):
     module.resolve_env_variables(config)
     assert config == {'key': 'Hello foo'}
 
+
 def test_env_multi(monkeypatch):
     monkeypatch.setenv('MY_CUSTOM_VALUE', 'foo')
     monkeypatch.setenv('MY_CUSTOM_VALUE2', 'bar')
@@ -23,6 +24,7 @@ def test_env_multi(monkeypatch):
     module.resolve_env_variables(config)
     assert config == {'key': 'Hello foobar'}
 
+
 def test_env_escape(monkeypatch):
     monkeypatch.setenv('MY_CUSTOM_VALUE', 'foo')
     monkeypatch.setenv('MY_CUSTOM_VALUE2', 'bar')