diff --git a/pyproject.toml b/black.toml
rename from pyproject.toml
rename to black.toml
diff --git a/contrib/examples/fix.hgrc b/contrib/examples/fix.hgrc
--- a/contrib/examples/fix.hgrc
+++ b/contrib/examples/fix.hgrc
@@ -11,5 +11,5 @@
 # git+https://github.com/python/black/@d9e71a75ccfefa3d9156a64c03313a0d4ad981e5
 # to have the dependencies for grey.
 #
-# black:command = python3.7 contrib/grey.py --quiet --skip-string-normalization -
+# black:command = python3.7 contrib/grey.py --quiet --config=black.toml --skip-string-normalization -
 # black:pattern = set:**.py - hgext/fsmonitor/pywatchman/** - mercurial/thirdparty/** - "contrib/python-zstandard/**"
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
@@ -64,10 +64,10 @@
   COPYING
   Makefile
   README.rst
+  black.toml
   hg
   hgeditor
   hgweb.cgi
-  pyproject.toml
   setup.py
 
 Prevent adding modules which could be shadowed by ancient .so/.dylib.