diff --git a/raid/raid.h b/raid/raid.h
index 89360018..b8012797 100644
--- a/raid/raid.h
+++ b/raid/raid.h
@@ -4,6 +4,8 @@
 #ifndef __RAID_H
 #define __RAID_H
 
+#include <stddef.h>
+
 /*
  * GF(2^8) reducing polynomial selection.
  *