diff --git a/pyproject.toml b/pyproject.toml
index d6262405bf633731229247e5e79c97b06ae24bbd..0af6b23c01b4014a568c5545b279291172e481f5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -62,6 +62,10 @@ pytest-sugar = "^0.9.2"
 [tool.poetry.plugins."aleksis.app"]
 chronos = "aleksis.apps.chronos.apps:ChronosConfig"
 
+[tool.black]
+line-length = 100
+exclude = "/migrations/"
+
 [build-system]
 requires = ["poetry>=1.0"]
 build-backend = "poetry.masonry.api"