diff --git a/kal/posix/src/pthread_mutex.c b/kal/posix/src/pthread_mutex.c
index 60ecc71b..a2459d94 100644
--- a/kal/posix/src/pthread_mutex.c
+++ b/kal/posix/src/pthread_mutex.c
@@ -134,6 +134,7 @@ int pthread_mutex_destroy(pthread_mutex_t *mutex)
         return MapError(ret);
     }
     mutex->handle = _MUX_INVALID_HANDLE;
+    mutex->magic = 0;
     return 0;
 }