diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -264,16 +264,6 @@
 _LIBCPP_THREAD_ABI_VISIBILITY
 void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns);
 
-struct __libcpp_timed_backoff_policy {
-  _LIBCPP_THREAD_ABI_VISIBILITY
-  bool operator()(chrono::nanoseconds __elapsed) const;
-};
-
-template<class _Fn, class _BFn>
-_LIBCPP_INLINE_VISIBILITY
-bool __libcpp_thread_poll_with_backoff(
-  _Fn && __f, _BFn && __bf, chrono::nanoseconds __max_elapsed = chrono::nanoseconds::zero());
-
 // Thread local storage
 _LIBCPP_THREAD_ABI_VISIBILITY
 int __libcpp_tls_create(__libcpp_tls_key* __key,
@@ -290,6 +280,16 @@
 #if (!defined(_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL) || \
      defined(_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL))
 
+struct __libcpp_timed_backoff_policy {
+  _LIBCPP_THREAD_ABI_VISIBILITY
+  bool operator()(chrono::nanoseconds __elapsed) const;
+};
+
+template<class _Fn, class _BFn>
+_LIBCPP_INLINE_VISIBILITY
+bool __libcpp_thread_poll_with_backoff(
+  _Fn && __f, _BFn && __bf, chrono::nanoseconds __max_elapsed = chrono::nanoseconds::zero());
+
 namespace __thread_detail {
 
 inline __libcpp_timespec_t __convert_to_timespec(const chrono::nanoseconds& __ns)