diff --git a/pyproject.toml b/pyproject.toml
index 25138f0..6bd3512 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -93,7 +93,7 @@ dependencies = [
 [project.optional-dependencies]
 develop = [
   "black<24",
-  "mypy<1.8",
+  "mypy<1.9",
   "poethepoet<0.25",
   "pyproject-fmt<1.6",
   "ruff==0.1.7",