diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
index 026429f6a8ec0b..dbf313a1bf22f1 100644
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -445,7 +445,7 @@ int __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
 
 int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m)
 {
-  return mtx_init(__m, mtx_recursive) == thrd_success ? 0 : EINVAL;
+  return mtx_init(__m, mtx_plain | mtx_recursive) == thrd_success ? 0 : EINVAL;
 }
 
 int __libcpp_recursive_mutex_lock(__libcpp_recursive_mutex_t *__m)