diff --git a/test_suite/tests/test_macros.rs b/test_suite/tests/test_macros.rs
index d18b210e..d4456bed 100644
--- a/test_suite/tests/test_macros.rs
+++ b/test_suite/tests/test_macros.rs
@@ -637,8 +637,10 @@ fn test_untagged_enum() {
         ],
     );
 
+    // Serializes to unit, deserializes from either depending on format's
+    // preference.
     assert_tokens(&Untagged::C, &[Token::Unit]);
-    assert_tokens(&Untagged::C, &[Token::None]);
+    assert_de_tokens(&Untagged::C, &[Token::None]);
 
     assert_tokens(&Untagged::D(4), &[Token::U8(4)]);
     assert_tokens(&Untagged::E("e".to_owned()), &[Token::Str("e")]);