diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 383c467..b03ff3c 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -5,6 +5,12 @@ repos:
     -   id: end-of-file-fixer
     -   id: trailing-whitespace
         exclude: ^tests/fixtures/diffs/
+-   repo: https://github.com/psf/black
+    rev: 20.8b1
+    hooks:
+    -   id: black
+        args: [--line-length=78]
+        files: ^src/
 -   repo: https://github.com/pre-commit/mirrors-mypy
     rev: v0.720
     hooks:
diff --git a/src/flake8/api/legacy.py b/src/flake8/api/legacy.py
index 68df9a2..7923698 100644
--- a/src/flake8/api/legacy.py
+++ b/src/flake8/api/legacy.py
@@ -41,7 +41,8 @@ def get_style_guide(**kwargs):
     application.find_plugins(config_finder)
     application.register_plugin_options()
     application.parse_configuration_and_cli(
-        config_finder, remaining_args,
+        config_finder,
+        remaining_args,
     )
     # We basically want application.initialize to be called but with these
     # options set instead before we make our formatter, notifier, internal
diff --git a/src/flake8/main/application.py b/src/flake8/main/application.py
index e4b7930..5c9e076 100644
--- a/src/flake8/main/application.py
+++ b/src/flake8/main/application.py
@@ -180,7 +180,9 @@ class Application(object):
             Command-line arguments passed in directly.
         """
         self.options, self.args = aggregator.aggregate_options(
-            self.option_manager, config_finder, argv,
+            self.option_manager,
+            config_finder,
+            argv,
         )
 
         self.running_against_diff = self.options.diff
@@ -328,7 +330,8 @@ class Application(object):
         self.find_plugins(config_finder)
         self.register_plugin_options()
         self.parse_configuration_and_cli(
-            config_finder, remaining_args,
+            config_finder,
+            remaining_args,
         )
         self.make_formatter()
         self.make_guide()
diff --git a/tox.ini b/tox.ini
index 489cfb1..76a2ead 100644
--- a/tox.ini
+++ b/tox.ini
@@ -32,15 +32,6 @@ commands =
     flake8 --version
     flake8 src/flake8/ tests/ setup.py
 
-# Autoformatter
-[testenv:black]
-basepython = python3
-skip_install = true
-deps =
-    black>=19.3b0
-commands =
-    black --line-length 78 src/
-
 # Linters
 [testenv:flake8]
 basepython = python3
@@ -93,14 +84,12 @@ commands =
 basepython = python3
 skip_install = true
 deps =
-    {[testenv:black]deps}
     {[testenv:flake8]deps}
     {[testenv:pylint]deps}
     {[testenv:doc8]deps}
     {[testenv:readme]deps}
     {[testenv:bandit]deps}
 commands =
-    {[testenv:black]commands}
     {[testenv:flake8]commands}
     {[testenv:pylint]commands}
     {[testenv:doc8]commands}