diff --git a/ompi/mca/io/base/io_base_request.c b/ompi/mca/io/base/io_base_request.c
index 710fef9d46..bdc4185995 100644
--- a/ompi/mca/io/base/io_base_request.c
+++ b/ompi/mca/io/base/io_base_request.c
@@ -19,6 +19,9 @@
 #ifdef HAVE_SYS_TIME_H
 #include <sys/time.h>
 #endif
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 
 #include "opal/class/opal_object.h"
 #include "file/file.h"