diff --git a/include/thread b/include/thread
index 6024456..c9d1dfa 100644
--- a/include/thread
+++ b/include/thread
@@ -424,7 +424,7 @@
 namespace this_thread
 {
 
-_LIBCPP_FUNC_VIS void sleep_for(const chrono::nanoseconds& ns);
+_LIBCPP_FUNC_VIS void sleep_for(const chrono::nanoseconds& __ns);
 
 template <class _Rep, class _Period>
 void