diff --git a/serde/src/private/de.rs b/serde/src/private/de.rs
index ffa5012d..1c7fda3a 100644
--- a/serde/src/private/de.rs
+++ b/serde/src/private/de.rs
@@ -2510,6 +2510,13 @@ mod content {
         {
             Ok(())
         }
+
+        fn visit_none<E>(self) -> Result<(), E>
+        where
+            E: de::Error,
+        {
+            Ok(())
+        }
     }
 }
 
diff --git a/test_suite/tests/test_macros.rs b/test_suite/tests/test_macros.rs
index c4eb06f3..d4456bed 100644
--- a/test_suite/tests/test_macros.rs
+++ b/test_suite/tests/test_macros.rs
@@ -637,7 +637,10 @@ fn test_untagged_enum() {
         ],
     );
 
+    // Serializes to unit, deserializes from either depending on format's
+    // preference.
     assert_tokens(&Untagged::C, &[Token::Unit]);
+    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")]);
@@ -652,11 +655,6 @@ fn test_untagged_enum() {
         ],
     );
 
-    assert_de_tokens_error::<Untagged>(
-        &[Token::None],
-        "data did not match any variant of untagged enum Untagged",
-    );
-
     assert_de_tokens_error::<Untagged>(
         &[Token::Tuple { len: 1 }, Token::U8(1), Token::TupleEnd],
         "data did not match any variant of untagged enum Untagged",