diff --git a/pyproject.toml b/pyproject.toml
index d662502..985f988 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,6 +24,7 @@ requires = ["pdm-backend"]
 build-backend = "pdm.backend"
 
 [tool.black]
+line-length = 88
 
 [tool.mypy]
 disallow_untyped_defs = true