diff --git a/black.toml b/black.toml
new file mode 100644
--- /dev/null
+++ b/black.toml
@@ -0,0 +1,14 @@
+[tool.black]
+line-length = 80
+exclude = '''
+build/
+| wheelhouse/
+| dist/
+| packages/
+| \.hg/
+| \.mypy_cache/
+| \.venv/
+| mercurial/thirdparty/
+'''
+skip-string-normalization = true
+quiet = true
diff --git a/contrib/examples/fix.hgrc b/contrib/examples/fix.hgrc
--- a/contrib/examples/fix.hgrc
+++ b/contrib/examples/fix.hgrc
@@ -5,7 +5,7 @@
 rustfmt:command = rustfmt +nightly
 rustfmt:pattern = set:"**.rs" - "mercurial/thirdparty/**"
 
-black:command = black
+black:command = black --config=black.toml -
 black:pattern = set:**.py - mercurial/thirdparty/**
 
 # Mercurial doesn't have any Go code, but if we did this is how we
diff --git a/pyproject.toml b/pyproject.toml
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,18 +1,3 @@
 [build-system]
 requires = ["setuptools", "wheel"]
 build-backend = "setuptools.build_meta"
-
-[tool.black]
-line-length = 80
-exclude = '''
-build/
-| wheelhouse/
-| dist/
-| packages/
-| \.hg/
-| \.mypy_cache/
-| \.venv/
-| mercurial/thirdparty/
-'''
-skip-string-normalization = true
-quiet = true
diff --git a/tests/test-check-code.t b/tests/test-check-code.t
--- a/tests/test-check-code.t
+++ b/tests/test-check-code.t
@@ -66,6 +66,7 @@
   COPYING
   Makefile
   README.rst
+  black.toml
   hg
   hgeditor
   hgweb.cgi
diff --git a/tests/test-check-format.t b/tests/test-check-format.t
--- a/tests/test-check-format.t
+++ b/tests/test-check-format.t
@@ -1,5 +1,5 @@
 #require black test-repo
 
   $ cd $RUNTESTDIR/..
-  $ black --check --diff `hg files 'set:(**.py + grep("^#!.*python")) - mercurial/thirdparty/**'`
+  $ black --config=black.toml --check --diff `hg files 'set:(**.py + grep("^#!.*python")) - mercurial/thirdparty/**'`