diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -420,7 +420,13 @@
 _LIBCPP_HIDE_FROM_ABI inline
 int __libcpp_thread_detach(__libcpp_thread_t *__t)
 {
+#if !defined(__MVS__) || defined( __SUSV3_THR)
   return pthread_detach(*__t);
+#elif defined(_OPEN_THREADS)
+  return pthread_detach(__t);
+#else
+  #error pthread_detach function is not available
+#endif
 }
 
 _LIBCPP_HIDE_FROM_ABI inline
@@ -446,7 +452,13 @@
 _LIBCPP_HIDE_FROM_ABI inline
 void *__libcpp_tls_get(__libcpp_tls_key __key)
 {
+#if !defined(__MVS__) || defined( __SUSV3_THR)
   return pthread_getspecific(__key);
+#elif defined(_OPEN_THREADS)
+  return pthread_getspecific_d8_np(__key);
+#else
+  #error pthread_getspecific function is not available
+#endif
 }
 
 _LIBCPP_HIDE_FROM_ABI inline