diff --git a/rosidl_generator_c/resource/full__description.c.em b/rosidl_generator_c/resource/full__description.c.em
index c146e1643..b506acfec 100644
--- a/rosidl_generator_c/resource/full__description.c.em
+++ b/rosidl_generator_c/resource/full__description.c.em
@@ -77,8 +77,16 @@ static const rosidl_type_hash_t @(c_typename)__EXPECTED_HASH = @(type_hash_to_c_
 
 @#<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
 @# Names for all types
+@{
+added_itype_names = set()
+}@
 @[for itype_description in all_type_descriptions]@
+@[  if itype_description['type_name'] not in added_itype_names]@
 static char @(typename_to_c(itype_description['type_name']))__TYPE_NAME[] = "@(itype_description['type_name'])";
+@{
+added_itype_names.add(itype_description['type_name'])
+}@
+@[  end if]@
 @[end for]@
 @#>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 
diff --git a/rosidl_generator_c/resource/msg__struct.h.em b/rosidl_generator_c/resource/msg__struct.h.em
index 23414ed45..fc7cf2dcf 100644
--- a/rosidl_generator_c/resource/msg__struct.h.em
+++ b/rosidl_generator_c/resource/msg__struct.h.em
@@ -150,6 +150,19 @@ enum
 @[end if]@
 @#>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 
+@#<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
+// forward declare type
+struct @(idl_structure_type_to_c_typename(message.structure.namespaced_type));
+// Struct for a sequence of @(idl_structure_type_to_c_typename(message.structure.namespaced_type)).
+typedef struct @(idl_structure_type_sequence_to_c_typename(message.structure.namespaced_type))
+{
+  struct @(idl_structure_type_to_c_typename(message.structure.namespaced_type)) * data;
+  /// The number of valid items in data
+  size_t size;
+  /// The number of allocated items in data
+  size_t capacity;
+} @(idl_structure_type_sequence_to_c_typename(message.structure.namespaced_type));
+
 @#<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
 /// Struct defined in @(interface_path_to_string(interface_path)) in the package @(package_name).
 @{comments = message.structure.get_comment_lines()}@
@@ -179,13 +192,3 @@ typedef struct @(idl_structure_type_to_c_typename(message.structure.namespaced_t
 } @(idl_structure_type_to_c_typename(message.structure.namespaced_type));
 @#>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 
-@#<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
-// Struct for a sequence of @(idl_structure_type_to_c_typename(message.structure.namespaced_type)).
-typedef struct @(idl_structure_type_sequence_to_c_typename(message.structure.namespaced_type))
-{
-  @(idl_structure_type_to_c_typename(message.structure.namespaced_type)) * data;
-  /// The number of valid items in data
-  size_t size;
-  /// The number of allocated items in data
-  size_t capacity;
-} @(idl_structure_type_sequence_to_c_typename(message.structure.namespaced_type));
diff --git a/rosidl_generator_type_description/rosidl_generator_type_description/__init__.py b/rosidl_generator_type_description/rosidl_generator_type_description/__init__.py
index a940a04fb..0da2661ee 100644
--- a/rosidl_generator_type_description/rosidl_generator_type_description/__init__.py
+++ b/rosidl_generator_type_description/rosidl_generator_type_description/__init__.py
@@ -471,7 +471,8 @@ def calculate_type_hash(serialized_type_description):
         del field['default_value']
     for referenced_td in hashable_dict['referenced_type_descriptions']:
         for field in referenced_td['fields']:
-            del field['default_value']
+            if 'default_value' in field:
+                del field['default_value']
 
     hashable_repr = json.dumps(
         hashable_dict,
diff --git a/rosidl_typesupport_introspection_cpp/resource/msg__type_support.cpp.em b/rosidl_typesupport_introspection_cpp/resource/msg__type_support.cpp.em
index 679907386..68662f21c 100644
--- a/rosidl_typesupport_introspection_cpp/resource/msg__type_support.cpp.em
+++ b/rosidl_typesupport_introspection_cpp/resource/msg__type_support.cpp.em
@@ -45,6 +45,18 @@ header_files = [
 @[    end if]@
 #include "@(header_file)"
 @[end for]@
+
+
+namespace rosidl_typesupport_introspection_cpp
+{
+
+template<>
+ROSIDL_TYPESUPPORT_INTROSPECTION_CPP_PUBLIC
+const rosidl_message_type_support_t *
+get_message_type_support_handle<@('::'.join([package_name] + list(interface_path.parents[0].parts) + [message.structure.namespaced_type.name]))>();
+
+}  // namespace rosidl_typesupport_introspection_cpp
+
 @[for ns in message.structure.namespaced_type.namespaces]@
 
 namespace @(ns)