diff --git a/lib/System/RWMutex.cpp b/lib/System/RWMutex.cpp
index 5a33364aa50..deb04709d82 100644
--- a/lib/System/RWMutex.cpp
+++ b/lib/System/RWMutex.cpp
@@ -73,6 +73,7 @@ RWMutexImpl::RWMutexImpl()
 
     // Initialize the rwlock
     int errorcode = pthread_rwlock_init(rwlock, NULL);
+    (void)errorcode;
     assert(errorcode == 0);
 
     // Assign the data member