diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index 664cbd958323b19bb9cb96470fdbb7274a007499..6d5ea0bdf1a3eba7ca5aab55a22ab78107734a3c 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -683,6 +683,7 @@ out:
         virtio_notify(vdev, vq);
         g_free(elem);
         g_free(buf);
+        buf = NULL;
     }
 }