diff --git a/include/atomic b/include/atomic
index daf64b2..31385a2 100644
--- a/include/atomic
+++ b/include/atomic
@@ -530,6 +530,10 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#if !__has_feature(cxx_atomic)
+#error <atomic> is not implemented
+#else
+
 typedef enum memory_order
 {
     memory_order_relaxed, memory_order_consume, memory_order_acquire,
@@ -1502,6 +1506,8 @@
 #define ATOMIC_LONG_LOCK_FREE 0
 #define ATOMIC_LLONG_LOCK_FREE 0
 
+#endif  //  !__has_feature(cxx_atomic)
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_ATOMIC