diff --git a/io/iob_prefetch.c b/io/iob_prefetch.c
index eaa1508..b16db6f 100644
--- a/io/iob_prefetch.c
+++ b/io/iob_prefetch.c
@@ -1,5 +1,6 @@
 #include "iob_internal.h"
 #include <stdio.h>
+#include <sys/types.h>
 #include <sys/mman.h>
 
 void iob_prefetch(io_batch* b,uint64 bytes) {