diff --git a/pyproject.toml b/pyproject.toml
index 8ad86ae04..7d870f575 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -131,6 +131,7 @@ dev-dependencies = [
 disable_error_code = ["import-untyped"]
 exclude = "src/flyte/_protos/.*"
 ignore_missing_imports = true
+check_untyped_defs = true
 
 [tool.ty.rules]
 unused-ignore-comment = "warn"