diff --git a/src/core/jsonschema/known_walker.cc b/src/core/jsonschema/known_walker.cc
index a01578065..b31b23b53 100644
--- a/src/core/jsonschema/known_walker.cc
+++ b/src/core/jsonschema/known_walker.cc
@@ -1785,6 +1785,10 @@ auto handle_requires(const Vocabularies &vocabularies)
 
 auto handle_optional(const Vocabularies &vocabularies)
     -> const SchemaWalkerResult & {
+  CHECK_VOCABULARY(Known::JSON_Schema_Draft_2, make_set({JSON::Type::Object}),
+                   Assertion)
+  CHECK_VOCABULARY(Known::JSON_Schema_Draft_2_Hyper,
+                   make_set({JSON::Type::Object}), Assertion)
   CHECK_VOCABULARY(Known::JSON_Schema_Draft_1, make_set({JSON::Type::Object}),
                    Assertion)
   CHECK_VOCABULARY(Known::JSON_Schema_Draft_1_Hyper,
diff --git a/test/jsonschema/jsonschema_walker_draft2_test.cc b/test/jsonschema/jsonschema_walker_draft2_test.cc
index c6b5ce131..8c7182615 100644
--- a/test/jsonschema/jsonschema_walker_draft2_test.cc
+++ b/test/jsonschema/jsonschema_walker_draft2_test.cc
@@ -249,6 +249,18 @@ TEST(JSONSchema_walker_draft2, requires) {
             sourcemeta::core::make_set({sourcemeta::core::JSON::Type::Object}));
 }
 
+TEST(JSONSchema_walker_draft2, optional) {
+  using namespace sourcemeta::core;
+  const auto &result{schema_walker("optional", VOCABULARIES_DRAFT2)};
+  EXPECT_EQ(result.type, SchemaKeywordType::Assertion);
+  EXPECT_TRUE(result.vocabulary.has_value());
+  EXPECT_VOCABULARY_KNOWN(result.vocabulary.value(), JSON_Schema_Draft_2);
+  EXPECT_TRUE(result.dependencies.empty());
+  EXPECT_TRUE(result.order_dependencies.empty());
+  EXPECT_EQ(result.instances,
+            sourcemeta::core::make_set({sourcemeta::core::JSON::Type::Object}));
+}
+
 TEST(JSONSchema_walker_draft2, format) {
   using namespace sourcemeta::core;
   const auto &result{schema_walker("format", VOCABULARIES_DRAFT2)};
@@ -713,6 +725,19 @@ TEST(JSONSchema_walker_draft2, hyperschema_requires) {
             sourcemeta::core::make_set({sourcemeta::core::JSON::Type::Object}));
 }
 
+TEST(JSONSchema_walker_draft2, hyperschema_optional) {
+  using namespace sourcemeta::core;
+  const auto &result{
+      schema_walker("optional", VOCABULARIES_DRAFT2_HYPERSCHEMA)};
+  EXPECT_EQ(result.type, SchemaKeywordType::Assertion);
+  EXPECT_TRUE(result.vocabulary.has_value());
+  EXPECT_VOCABULARY_KNOWN(result.vocabulary.value(), JSON_Schema_Draft_2_Hyper);
+  EXPECT_TRUE(result.dependencies.empty());
+  EXPECT_TRUE(result.order_dependencies.empty());
+  EXPECT_EQ(result.instances,
+            sourcemeta::core::make_set({sourcemeta::core::JSON::Type::Object}));
+}
+
 TEST(JSONSchema_walker_draft2, hyperschema_format) {
   using namespace sourcemeta::core;
   const auto &result{schema_walker("format", VOCABULARIES_DRAFT2_HYPERSCHEMA)};