Index: libcxx/include/__threading_support
===================================================================
--- libcxx/include/__threading_support
+++ libcxx/include/__threading_support
@@ -79,7 +79,7 @@
 typedef pthread_key_t __libcpp_tls_key;
 
 #define _LIBCPP_TLS_DESTRUCTOR_CC
-#else
+#elif !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
 // Mutex
 typedef void* __libcpp_mutex_t;
 #define _LIBCPP_MUTEX_INITIALIZER 0
@@ -112,7 +112,6 @@
 typedef long __libcpp_tls_key;
 
 #define _LIBCPP_TLS_DESTRUCTOR_CC __stdcall
-#endif // defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
 
 // Mutex
 _LIBCPP_THREAD_ABI_VISIBILITY
@@ -208,6 +207,8 @@
 _LIBCPP_THREAD_ABI_VISIBILITY
 int __libcpp_tls_set(__libcpp_tls_key __key, void *__p);
 
+#endif // !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+
 #if (!defined(_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL) || \
      defined(_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL)) && \
     defined(_LIBCPP_HAS_THREAD_API_PTHREAD)