diff --git a/opal/util/path.h b/opal/util/path.h
index 0dcf4387f8..9373feb8d3 100644
--- a/opal/util/path.h
+++ b/opal/util/path.h
@@ -23,6 +23,10 @@
 
 #include "opal_config.h"
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 BEGIN_C_DECLS
 
 /**