diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index f09e6df15aa7..13d87a031c88 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -1184,6 +1184,7 @@ static int cciss_ioctl32_big_passthru(struct block_device *bdev, fmode_t mode,
 	int err;
 	u32 cp;
 
+	memset(&arg64, 0, sizeof(arg64));
 	err = 0;
 	err |=
 	    copy_from_user(&arg64.LUN_info, &arg32->LUN_info,