diff --git a/ompi/debuggers/dlopen_test.c b/ompi/debuggers/dlopen_test.c
index 266a1c2438..27ef62c5a6 100644
--- a/ompi/debuggers/dlopen_test.c
+++ b/ompi/debuggers/dlopen_test.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2015 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2009-2018 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -12,6 +12,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include "opal/runtime/opal.h"
 #include "opal/mca/dl/base/base.h"