diff --git a/pyproject.toml b/pyproject.toml
index 90ec106..b49b39d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,6 +3,7 @@ requires = ["setuptools"]
 build-backend = "setuptools.build_meta"
 
 [tool.black]
+line-length = 89
 include = '\.pyi?$'
 exclude = '''
 /(