diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index 7c54c6b..8fe69ab 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -563,10 +563,15 @@
     int ret = -EINVAL;
 
     if (!sbus) {
-        error_report("%s no sbus", __func__);
+        error_setg(errp, "%s: no IOMMUPciBus found!", __func__);
+        return ret;
     }
 
     sdev = sbus->pbdev[devfn];
+    if (!sdev) {
+        error_setg(errp, "%s: no IOMMUDevice found!", __func__);
+        return ret;
+    }
 
     current_ranges = sdev->host_resv_ranges;