diff --git a/serde/src/private/de.rs b/serde/src/private/de.rs
index 883e6909..c402d2c6 100644
--- a/serde/src/private/de.rs
+++ b/serde/src/private/de.rs
@@ -313,6 +313,8 @@ mod content {
         }
     }
 
+    /// Used to capture data in [`Content`] from other deserializers.
+    /// Cannot capture externally tagged enums, `i128` and `u128`.
     struct ContentVisitor<'de> {
         value: PhantomData<Content<'de>>,
     }
@@ -528,6 +530,8 @@ mod content {
         Content(Content<'de>),
     }
 
+    /// Serves as a seed for deserializing a key of internally tagged enum.
+    /// Cannot capture externally tagged enums, `i128` and `u128`.
     struct TagOrContentVisitor<'de> {
         name: &'static str,
         value: PhantomData<TagOrContent<'de>>,
@@ -814,6 +818,9 @@ mod content {
 
     /// Used by generated code to deserialize an internally tagged enum.
     ///
+    /// Captures map or sequence from the original deserializer and searches
+    /// a tag in it (in case of sequence, tag is the first element of sequence).
+    ///
     /// Not public API.
     pub struct TaggedContentVisitor<T> {
         tag_name: &'static str,
diff --git a/test_suite/tests/test_macros.rs b/test_suite/tests/test_macros.rs
index 02c36c41..0d6472df 100644
--- a/test_suite/tests/test_macros.rs
+++ b/test_suite/tests/test_macros.rs
@@ -1081,6 +1081,15 @@ fn test_internally_tagged_struct_variant_containing_unit_variant() {
         Log { level: Level },
     }
 
+    assert_de_tokens(
+        &Level::Info,
+        &[
+            Token::Enum { name: "Level" },
+            Token::BorrowedStr("Info"),
+            Token::Unit,
+        ],
+    );
+
     assert_de_tokens(
         &Message::Log { level: Level::Info },
         &[
@@ -1091,7 +1100,9 @@ fn test_internally_tagged_struct_variant_containing_unit_variant() {
             Token::Str("action"),
             Token::Str("Log"),
             Token::Str("level"),
+            Token::Enum { name: "Level" },
             Token::BorrowedStr("Info"),
+            Token::Unit,
             Token::StructEnd,
         ],
     );
@@ -1103,7 +1114,9 @@ fn test_internally_tagged_struct_variant_containing_unit_variant() {
             Token::Str("action"),
             Token::Str("Log"),
             Token::Str("level"),
+            Token::Enum { name: "Level" },
             Token::BorrowedStr("Info"),
+            Token::Unit,
             Token::MapEnd,
         ],
     );
@@ -1113,7 +1126,9 @@ fn test_internally_tagged_struct_variant_containing_unit_variant() {
         &[
             Token::Seq { len: Some(2) },
             Token::Str("Log"),
+            Token::Enum { name: "Level" },
             Token::BorrowedStr("Info"),
+            Token::Unit,
             Token::SeqEnd,
         ],
     );