diff --git a/include/boost/asio/detail/socket_types.hpp b/include/boost/asio/detail/socket_types.hpp
index adc36483f..1ebd1bb2f 100644
--- a/include/boost/asio/detail/socket_types.hpp
+++ b/include/boost/asio/detail/socket_types.hpp
@@ -414,7 +414,9 @@ const int max_iov_len = 16;
 # endif
 # define BOOST_ASIO_OS_DEF_SA_RESTART SA_RESTART
 # define BOOST_ASIO_OS_DEF_SA_NOCLDSTOP SA_NOCLDSTOP
-# define BOOST_ASIO_OS_DEF_SA_NOCLDWAIT SA_NOCLDWAIT
+# if defined(SA_NOCLDWAIT)
+#  define BOOST_ASIO_OS_DEF_SA_NOCLDWAIT SA_NOCLDWAIT
+# endif
 #endif
 const int custom_socket_option_level = 0xA5100000;
 const int enable_connection_aborted_option = 1;
diff --git a/include/boost/asio/signal_set_base.hpp b/include/boost/asio/signal_set_base.hpp
index 0f960cc86..5c3a2348b 100644
--- a/include/boost/asio/signal_set_base.hpp
+++ b/include/boost/asio/signal_set_base.hpp
@@ -65,7 +65,9 @@ class signal_set_base
     none = 0,
     restart = BOOST_ASIO_OS_DEF(SA_RESTART),
     no_child_stop = BOOST_ASIO_OS_DEF(SA_NOCLDSTOP),
+#if defined(BOOST_ASIO_OS_DEF_SA_NOCLDWAIT)
     no_child_wait = BOOST_ASIO_OS_DEF(SA_NOCLDWAIT),
+#endif
     dont_care = -1
   };