diff --git a/libcxx/src/mutex.cpp b/libcxx/src/mutex.cpp
index b858e88..338b79f 100644
--- a/libcxx/src/mutex.cpp
+++ b/libcxx/src/mutex.cpp
@@ -11,6 +11,7 @@
 #include "mutex"
 #include "limits"
 #include "system_error"
+#include "cassert"
 #include "include/atomic_support.h"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
@@ -44,7 +45,7 @@
 {
     int ec = __libcpp_mutex_unlock(&__m_);
     (void)ec;
-    _LIBCPP_ASSERT(ec == 0, "call to mutex::unlock failed");
+    assert(ec == 0);
 }
 
 // recursive_mutex
@@ -60,7 +61,7 @@
 {
     int e = __libcpp_recursive_mutex_destroy(&__m_);
     (void)e;
-    _LIBCPP_ASSERT(e == 0, "call to ~recursive_mutex() failed");
+    assert(e == 0);
 }
 
 void
@@ -76,7 +77,7 @@
 {
     int e = __libcpp_recursive_mutex_unlock(&__m_);
     (void)e;
-    _LIBCPP_ASSERT(e == 0, "call to recursive_mutex::unlock() failed");
+    assert(e == 0);
 }
 
 bool