diff --git a/tests/pthread_test.cpp b/tests/pthread_test.cpp
index 40059d0..8ac5223 100644
--- a/tests/pthread_test.cpp
+++ b/tests/pthread_test.cpp
@@ -1672,6 +1672,7 @@
 
   void destroy() {
     ASSERT_EQ(0, pthread_mutex_destroy(&lock));
+    ASSERT_EQ(EBUSY, pthread_mutex_destroy(&lock));
   }
 
   DISALLOW_COPY_AND_ASSIGN(PthreadMutex);