diff --git a/pyproject.toml b/pyproject.toml
index 901443c..e49dab6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,3 +19,4 @@ packages = []
 show_error_codes = true
 ignore_missing_imports = true
 warn_redundant_casts = true
+check_untyped_defs = true