diff --git a/src/json/include/sourcemeta/jsontoolkit/json_flat_map.h b/src/json/include/sourcemeta/jsontoolkit/json_flat_map.h
index 241aadd37..d9aa5d4b0 100644
--- a/src/json/include/sourcemeta/jsontoolkit/json_flat_map.h
+++ b/src/json/include/sourcemeta/jsontoolkit/json_flat_map.h
@@ -10,7 +10,6 @@
 
 namespace sourcemeta::jsontoolkit {
 
-// TODO: Merge as part of JSONObject
 /// @ingroup json
 template <typename Key, typename Value, typename Hash> class FlatMap {
 public:
@@ -53,8 +52,6 @@ template <typename Key, typename Value, typename Hash> class FlatMap {
     return this->hasher(key);
   }
 
-  // TODO: Add an assign overload for const key, rvalue
-
   auto assign(key_type &&key, mapped_type &&value) -> hash_type {
     const auto key_hash{this->hash(key)};
 
diff --git a/src/json/json_value.cc b/src/json/json_value.cc
index f8a2998cd..68bee18ab 100644
--- a/src/json/json_value.cc
+++ b/src/json/json_value.cc
@@ -587,7 +587,8 @@ JSON::at(const String &key,
   } else if (this->is_boolean()) {
     return sizeof(bool);
   } else {
-    return sizeof(std::nullptr_t);
+    // The size of the union
+    return 8;
   }
 }
 
diff --git a/test/json/json_null_test.cc b/test/json/json_null_test.cc
index b53ee70d1..c4ba2643b 100644
--- a/test/json/json_null_test.cc
+++ b/test/json/json_null_test.cc
@@ -21,8 +21,6 @@ TEST(JSON_null, literal_equality) {
 
 TEST(JSON_null, estimated_byte_size) {
   const sourcemeta::jsontoolkit::JSON document{nullptr};
-  // TODO: Use a different internal type for representing nulls,
-  // as this is otherwise 64 bytes?
   EXPECT_EQ(document.estimated_byte_size(), 8);
 }