diff --git a/fio.h b/fio.h
index 5dc0352..56aa9b6 100644
--- a/fio.h
+++ b/fio.h
@@ -373,6 +373,7 @@
 	struct timeval lastrate[2];
 
 	unsigned long long total_io_size;
+	unsigned long long fill_device_size;
 
 	unsigned long io_issues[2];
 	unsigned long long io_blocks[2];