diff --git a/block/qcow.c b/block/qcow.c
index 7280103..7b5ab87 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -569,7 +569,7 @@
 
     if (qiov->niov > 1) {
         buf = orig_buf = qemu_blockalign(bs, qiov->size);
-        qemu_iovec_to_buffer(qiov, buf);
+        qemu_iovec_to_buf(qiov, 0, buf, qiov->size);
     } else {
         orig_buf = NULL;
         buf = (uint8_t *)qiov->iov->iov_base;