diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 4e2de46d45..f678e26b28 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -8735,6 +8735,9 @@ virDomainDiskBackingStoreParse(xmlXPathContextPtr ctxt,
     if (VIR_ALLOC(backingStore) < 0)
         goto cleanup;
 
+    /* backing store is always read-only */
+    backingStore->readonly = true;
+
     /* terminator does not have a type */
     if (!(type = virXMLPropString(ctxt->node, "type"))) {
         VIR_STEAL_PTR(src->backingStore, backingStore);
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 83fc191085..c129321a5c 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -14680,6 +14680,9 @@ qemuDomainSnapshotUpdateDiskSources(qemuDomainSnapshotDiskDataPtr dd,
     if (dd->initialized)
         virStorageFileDeinit(dd->src);
 
+    /* the old disk image is now readonly */
+    dd->disk->src->readonly = true;
+
     VIR_STEAL_PTR(dd->disk->src->relPath, dd->relPath);
     VIR_STEAL_PTR(dd->src->backingStore, dd->disk->src);
     VIR_STEAL_PTR(dd->disk->src, dd->src);
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 185427f19c..b10a40e545 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -3425,6 +3425,7 @@ virStorageSourceNewFromBacking(virStorageSourcePtr parent)
         if (virStorageSourceInitChainElement(ret, parent, true) < 0)
             goto error;
 
+        ret->readonly = true;
         ret->detected = true;
     }