diff --git a/src/ioc/db/dbLock.h b/src/ioc/db/dbLock.h
index 1d6388ed3..e15ddd0e9 100644
--- a/src/ioc/db/dbLock.h
+++ b/src/ioc/db/dbLock.h
@@ -13,6 +13,8 @@
 #ifndef INCdbLockh
 #define INCdbLockh
 
+#include <stddef.h>
+
 #include "ellLib.h"
 #include "shareLib.h"