diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c
index 0473ae8..bd7a075 100644
--- a/hw/vfio_pci.c
+++ b/hw/vfio_pci.c
@@ -943,6 +943,8 @@ static void vfio_listener_region_add(MemoryListener *listener,
     void *vaddr;
     int ret;
 
+    assert(!memory_region_is_iommu(section->mr));
+
     if (vfio_listener_skipped_section(section)) {
         DPRINTF("vfio: SKIPPING region_add %"HWADDR_PRIx" - %"PRIx64"\n",
                 section->offset_within_address_space,