diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index 201127c488..4dcf1d5c62 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -728,13 +728,15 @@ static void virtio_iommu_handle_command(VirtIODevice *vdev, VirtQueue *vq)
     VirtIOIOMMU *s = VIRTIO_IOMMU(vdev);
     struct virtio_iommu_req_head head;
     struct virtio_iommu_req_tail tail = {};
-    size_t output_size = sizeof(tail), sz;
     VirtQueueElement *elem;
     unsigned int iov_cnt;
     struct iovec *iov;
     void *buf = NULL;
+    size_t sz;
 
     for (;;) {
+        size_t output_size = sizeof(tail);
+
         elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
         if (!elem) {
             return;