diff --git a/ridlbe/c++11/templates/cli/prx/struct_cdr.erb b/ridlbe/c++11/templates/cli/prx/struct_cdr.erb
index 86a94ebc..38b9d789 100644
--- a/ridlbe/c++11/templates/cli/prx/struct_cdr.erb
+++ b/ridlbe/c++11/templates/cli/prx/struct_cdr.erb
@@ -18,5 +18,26 @@ TAO_BEGIN_VERSIONED_NAMESPACE_DECL
 <%= stub_proxy_export_macro %>TAO_CORBA::Boolean operator<< (TAO_OutputCDR&, const <%= scoped_cxxname %>&);
 <%= stub_proxy_export_macro %>TAO_CORBA::Boolean operator>> (TAO_InputCDR&, <%= scoped_cxxname %>&);
 //@}
+%members.each do |_m|
+% if _m.optional?
+// Unaliased type : <%= _m.cxx_member_type %>
+% alias_md5 =  _m.cxx_member_type.to_md5
+// MD5            : <%= alias_md5 %>
+#if !defined(_CDR_<%= alias_md5 %>_OPTIONAL_DECL_)
+#define _CDR_<%= alias_md5 %>_OPTIONAL_DECL_
+/// @name CDR streaming operator specializations for <%= _m.cxx_member_type %>
+//@{
+inline <%= stub_proxy_export_macro %>TAO_CORBA::Boolean operator<< (TAO_OutputCDR& _strm, const <%= _m.cxx_member_type %>& _val)
+{
+  return taox11_optional_cdr<<%= _m.cxx_member_type %>>::insert (_strm,  _val);
+}
+<%= stub_proxy_export_macro %>TAO_CORBA::Boolean operator>> (TAO_InputCDR& _strm, <%= _m.cxx_member_type %>& _val)
+{
+  return taox11_optional_cdr<<%= _m.cxx_member_type %>>::extract (_strm,  _val);
+}
+//@}
+#endif
+% end
+%end
 
 TAO_END_VERSIONED_NAMESPACE_DECL
diff --git a/ridlbe/c++11/templates/cli/src/union_cdr.erb b/ridlbe/c++11/templates/cli/src/union_cdr.erb
index fb2fe042..e6a90852 100644
--- a/ridlbe/c++11/templates/cli/src/union_cdr.erb
+++ b/ridlbe/c++11/templates/cli/src/union_cdr.erb
@@ -2,7 +2,7 @@
 // generated from <%= ridl_template_path %>
 TAO_CORBA::Boolean operator<< (TAO_OutputCDR &strm, const <%= scoped_cxxname %> &_tao_union)
 {
-  if (!(strm <<<%= switchtype.cdr_from_fmt % "_tao_union._d ()" %>))
+  if (!(strm << <%= switchtype.cdr_from_fmt % "_tao_union._d ()" %>))
   {
     return false;
   }
diff --git a/ridlbe/c++11/visitors/struct.rb b/ridlbe/c++11/visitors/struct.rb
index 1ece1e28..c8aa5a64 100644
--- a/ridlbe/c++11/visitors/struct.rb
+++ b/ridlbe/c++11/visitors/struct.rb
@@ -123,7 +123,7 @@ def cxx_out_type
 
       def cxx_in_type
         if optional?
-          "const IDL::optional<#{super}>&"
+          "const IDL::optional<#{cxx_return_type}>&"
         elsif external?
           "const std::shared_ptr<#{super}>&"
         else
diff --git a/ridlbe/c++11/writers/stubproxyheader.rb b/ridlbe/c++11/writers/stubproxyheader.rb
index a0a658b1..d536362b 100644
--- a/ridlbe/c++11/writers/stubproxyheader.rb
+++ b/ridlbe/c++11/writers/stubproxyheader.rb
@@ -189,6 +189,7 @@ def enter_struct(node)
 
         add_include('tao/x11/basic_argument_t.h')
         node.members.each { |m| check_idl_type(m.idltype) }
+        node.members.each { |m| add_include('tao/x11/optional_cdr_t.h') if !m.annotations[:optional].first.nil? }
       end
 
       def enter_union(node)
diff --git a/tao/x11/base/bounded_map_t.h b/tao/x11/base/bounded_map_t.h
index 6750d2be..609af3f4 100644
--- a/tao/x11/base/bounded_map_t.h
+++ b/tao/x11/base/bounded_map_t.h
@@ -44,10 +44,8 @@ namespace TAOX11_NAMESPACE
       using size_type = typename _Map::size_type;
       using difference_type = typename _Map::difference_type;
       using allocator_type = typename _Map::allocator_type;
-#if defined (ACE_HAS_CPP17)
       using node_type = typename _Map::node_type;
       using insert_return_type = typename _Map::insert_return_type;
-#endif /* ACE_HAS_CPP17 */
 
       using bound = std::integral_constant<uint32_t, _Bound>;
 
diff --git a/tao/x11/optional_cdr_t.h b/tao/x11/optional_cdr_t.h
new file mode 100644
index 00000000..37a09326
--- /dev/null
+++ b/tao/x11/optional_cdr_t.h
@@ -0,0 +1,70 @@
+/**
+ * @file    optional_cdr_t.h
+ * @author  Johnny Willemsen
+ *
+ * @brief   x11 optional marshaling templates
+ *
+ * @copyright Copyright (c) Remedy IT Expertise BV
+ */
+
+#ifndef TAOX11_OPTIONAL_CDR_T_H_INCLUDED
+#define TAOX11_OPTIONAL_CDR_T_H_INCLUDED
+
+#include "tao/x11/base/tao_corba.h"
+
+TAO_BEGIN_VERSIONED_NAMESPACE_DECL
+
+  /// Generic sequence CDR streaming helper template
+  template <typename _Tp>
+  struct taox11_optional_cdr
+  {
+    /// Unbounded insert
+    template <typename _Stream>
+    static bool insert (_Stream& _strm, const _Tp& _optional)
+    {
+      if (!(_strm << ACE_OutputCDR::from_boolean (_optional.has_value ())))
+      {
+        return false;
+      }
+
+      bool result { true };
+      if (_optional.has_value ())
+      {
+        result = _strm << _optional.value ();
+      }
+      return result;
+    }
+
+    /// Unbounded extract
+    template <typename _Stream>
+    static bool extract (_Stream& _strm, _Tp& _optional)
+    {
+      bool _has_value{};
+      if (!(_strm >> ACE_InputCDR::to_boolean (_has_value)))
+      {
+        return false;
+      }
+
+      if (_has_value)
+      {
+        // initialize associated default value
+        typename _Tp::value_type temp_val{};
+        // extract
+        if (_strm >> temp_val)
+        {
+          // set union member and associated discriminant when there are multiple legal discriminant values
+          _optional = std::move (temp_val);
+          return true;
+        }
+      }
+      else
+      {
+        _optional.reset ();
+      }
+      return false;
+    }
+  };
+
+TAO_END_VERSIONED_NAMESPACE_DECL
+
+#endif // TAOX11_OPTIONAL_CDR_T_H_INCLUDED
diff --git a/tao/x11/optional_t.h b/tao/x11/optional_t.h
index aff68909..be47fd21 100644
--- a/tao/x11/optional_t.h
+++ b/tao/x11/optional_t.h
@@ -3,7 +3,7 @@
  * @file   optional_t.h
  * @author Johnny Willemsen
  *
- * @brief template for IDL4 optional annotaiton
+ * @brief template for IDL4 optional annotation
  *
  * @copyright Copyright (c) Remedy IT Expertise BV
  */
@@ -14,8 +14,6 @@
 #include <optional>
 #include "tao/x11/base/versioned_x11_namespace.h"
 
-#if defined (ACE_HAS_CPP17)
-
 namespace TAOX11_NAMESPACE
 {
   namespace IDL
@@ -25,20 +23,4 @@ namespace TAOX11_NAMESPACE
   } // namespace IDL
 } // namespace TAOX11_NAMESPACE
 
-#else
-
-namespace TAOX11_NAMESPACE
-{
-  namespace IDL
-  {
-    template<typename T>
-    class optional
-    {
-    public:
-      T value_;
-    };
-  }
-}
-#endif
-
 #endif // __IDL__OPTIONAL_T_H_INCLUDED__
diff --git a/tao/x11/portable_server/operation_table_std_map.h b/tao/x11/portable_server/operation_table_std_map.h
index 1d804abb..93171d54 100644
--- a/tao/x11/portable_server/operation_table_std_map.h
+++ b/tao/x11/portable_server/operation_table_std_map.h
@@ -72,11 +72,7 @@ class TAOX11_PortableServer_Export Std_Map_OpTable final
             const TAO::Operation_Skeletons skel_ptr) override;
 
 private:
-#if defined (ACE_HAS_CPP17)
   using key_map_type = std::string_view ;
-#else
-  using key_map_type = std::string ;
-#endif /* ACE_HAS_CPP17 */
 
   using map_type = std::unordered_map<key_map_type, TAO::Operation_Skeletons>;
 
diff --git a/tao/x11/taox11.mpc b/tao/x11/taox11.mpc
index b29487de..ee29a608 100644
--- a/tao/x11/taox11.mpc
+++ b/tao/x11/taox11.mpc
@@ -312,6 +312,8 @@ project(taox11) : taox11_defaults, taolib {
     object_ostream.h
     object_traits_t.h
     objproxy.h
+    optional_t.h
+    optional_cdr_t.h
     orb.h
     orb_constants.h
     orb_registry.h
diff --git a/tests/idl4/optional/test.idl b/tests/idl4/optional/test.idl
index 5afcbc71..e47e3521 100644
--- a/tests/idl4/optional/test.idl
+++ b/tests/idl4/optional/test.idl
@@ -10,5 +10,6 @@ struct bar
   short x;
   string y;
   @optional short z;
+  @optional short a;
+  @optional string opt_string;
 };
-
diff --git a/tests/idl4/optional/test.mpc b/tests/idl4/optional/test.mpc
index 0607b3c3..66bd2e3b 100644
--- a/tests/idl4/optional/test.mpc
+++ b/tests/idl4/optional/test.mpc
@@ -3,7 +3,7 @@
 project(*optional_gen_idl): ridl_ostream_defaults {
   IDL_Files {
     test.idl
-    idlflags += --idl-version=4 -Scdr
+    idlflags += --idl-version=4
   }
   custom_only = 1
 }
diff --git a/tests/interface/client.cpp b/tests/interface/client.cpp
index a22c777f..9113ea93 100644
--- a/tests/interface/client.cpp
+++ b/tests/interface/client.cpp
@@ -61,7 +61,6 @@ int main(int argc, char* argv[])
       IDL::traits<CORBA::Object>::ref_type obj2;
       std::swap (obj, obj2);
       std::swap (obj, obj2);
-#if defined (ACE_HAS_CPP17)
       if (!std::is_swappable<IDL::traits<CORBA::Object>::ref_type>())
       {
         TAOX11_TEST_ERROR << "ERROR: IDL::traits<CORBA::Object>::ref_type is not swappable." << std::endl;
@@ -71,7 +70,6 @@ int main(int argc, char* argv[])
       {
         TAOX11_TEST_DEBUG << "IDL::traits<CORBA::Object>::ref_type is swappable." << std::endl;
       }
-#endif /* ACE_HAS_CPP17 */
 
       if (!test_nil_invocation())
         ++result;
diff --git a/tests/struct/client.cpp b/tests/struct/client.cpp
index 2c79208e..5ca32df9 100644
--- a/tests/struct/client.cpp
+++ b/tests/struct/client.cpp
@@ -106,7 +106,6 @@ int main(int argc, char* argv[])
       V s5;
       V s6;
       test_swap (s5, s6);
-#if defined (ACE_HAS_CPP17)
       if (!std::is_swappable<V>())
       {
         TAOX11_TEST_ERROR << "ERROR: V is not swappable." << std::endl;
@@ -116,7 +115,6 @@ int main(int argc, char* argv[])
       {
         TAOX11_TEST_DEBUG << "V is swappable." << std::endl;
       }
-#endif /* ACE_HAS_CPP17 */
 
       TAOX11_TEST_DEBUG << "successfully called Foo::update_struct (" << simple3 << ") => " << simple4 << std::endl;
 
diff --git a/tests/union/client.cpp b/tests/union/client.cpp
index 24150340..64e2db25 100644
--- a/tests/union/client.cpp
+++ b/tests/union/client.cpp
@@ -26,7 +26,6 @@ test_data_union (IDL::traits<Test::Foo>::ref_type foo)
   data.pointData (Test::Point (12, 34));
   retval += check_union (data, Test::DataType::dtPoint, "before pass_union");
 
-#if defined (ACE_HAS_CPP17)
   if (!std::is_swappable<Test::Data>())
   {
     TAOX11_TEST_ERROR << "ERROR: V is not swappable." << std::endl;
@@ -36,7 +35,6 @@ test_data_union (IDL::traits<Test::Foo>::ref_type foo)
   {
     TAOX11_TEST_DEBUG << "Test::Data is swappable." << std::endl;
   }
-#endif /* ACE_HAS_CPP17 */
 
   if (foo->pass_union (data))
   {