diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index d2d95ff5353b08a4f49d1c3da4179090751851bf..edfa2515bc8613f952c448194bfcebf7835d75c1 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -1189,6 +1189,7 @@ static int cciss_ioctl32_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,