diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -390,7 +390,7 @@
   return pthread_mutex_trylock(__m) == 0;
 }
 
-int __libcpp_recursive_mutex_unlock(__libcpp_mutex_t *__m)
+int __libcpp_recursive_mutex_unlock(__libcpp_recursive_mutex_t *__m)
 {
   return pthread_mutex_unlock(__m);
 }
@@ -578,7 +578,7 @@
   return mtx_trylock(__m) == thrd_success;
 }
 
-int __libcpp_recursive_mutex_unlock(__libcpp_mutex_t *__m)
+int __libcpp_recursive_mutex_unlock(__libcpp_recursive_mutex_t *__m)
 {
   return mtx_unlock(__m) == thrd_success ? 0 : EINVAL;
 }