diff --git a/serde_with/tests/serde_as/map_tuple_list.rs b/serde_with/tests/serde_as/map_tuple_list.rs
index 59b00d61..f0957b81 100644
--- a/serde_with/tests/serde_as/map_tuple_list.rs
+++ b/serde_with/tests/serde_as/map_tuple_list.rs
@@ -353,6 +353,8 @@ fn test_map_as_tuple_with_nested_complex_type() {
     );
 }
 
+// Problematic handling around fundamental types: https://github.com/rust-lang/rust/issues/121621
+#[allow(unknown_lints, non_local_definitions)]
 #[test]
 fn test_map_as_tuple_list_works_with_serializer_that_needs_length_to_serialize_sequence() {
     use serde::{