diff --git a/pyproject.toml b/pyproject.toml
index c6eabfb4958ebddade085e65f4ba3e1909eb306e..b386799e43570a86035d5d8df5213015c2133d07 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -65,6 +65,10 @@ pytest-sugar = "^0.9.2"
 [tool.poetry.plugins."aleksis.app"]
 untis = "aleksis.apps.untis.apps:UntisConfig"
 
+[tool.black]
+line-length = 100
+exclude = "/migrations/"
+
 [build-system]
 requires = ["poetry>=0.12"]
 build-backend = "poetry.masonry.api"