diff --git a/flux/example_code/mpi_hellosleep.c b/flux/example_code/mpi_hellosleep.c
index ea64a95..b5418bd 100644
--- a/flux/example_code/mpi_hellosleep.c
+++ b/flux/example_code/mpi_hellosleep.c
@@ -1,6 +1,7 @@
 #include "mpi.h"
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #define  MASTER		0
 
 int main (int argc, char *argv[])