diff --git a/mypy.ini b/mypy.ini
index b99c5a5..aecd40e 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -5,3 +5,4 @@ strict_optional = True
 warn_unused_ignores = False
 warn_redundant_casts = True
 warn_unused_configs = True
+disallow_untyped_defs = True