diff --git a/tests/domainbackupxml2xmlout/backup-pull-encrypted.xml b/tests/domainbackupxml2xmlout/backup-pull-encrypted.xml
index ea9dcf72b9..3c3042111d 100644
--- a/tests/domainbackupxml2xmlout/backup-pull-encrypted.xml
+++ b/tests/domainbackupxml2xmlout/backup-pull-encrypted.xml
@@ -26,5 +26,6 @@
         </encryption>
       </scratch>
     </disk>
+    <disk name='vdextradisk' backup='no'/>
   </disks>
 </domainbackup>
diff --git a/tests/domainbackupxml2xmlout/backup-pull-internal-invalid.xml b/tests/domainbackupxml2xmlout/backup-pull-internal-invalid.xml
index ba8f7ca3ab..9702978ce0 100644
--- a/tests/domainbackupxml2xmlout/backup-pull-internal-invalid.xml
+++ b/tests/domainbackupxml2xmlout/backup-pull-internal-invalid.xml
@@ -26,6 +26,7 @@
         </encryption>
       </scratch>
     </disk>
+    <disk name='vdextradisk' backup='no'/>
   </disks>
   <privateData>
     <objects>
diff --git a/tests/domainbackupxml2xmlout/backup-pull-seclabel.xml b/tests/domainbackupxml2xmlout/backup-pull-seclabel.xml
index 450f007d3a..38330394f7 100644
--- a/tests/domainbackupxml2xmlout/backup-pull-seclabel.xml
+++ b/tests/domainbackupxml2xmlout/backup-pull-seclabel.xml
@@ -14,5 +14,6 @@
         <seclabel model='dac' relabel='no'/>
       </scratch>
     </disk>
+    <disk name='vdextradisk' backup='no'/>
   </disks>
 </domainbackup>
diff --git a/tests/domainbackupxml2xmlout/backup-pull.xml b/tests/domainbackupxml2xmlout/backup-pull.xml
index 24fce9c0e7..4952270a5a 100644
--- a/tests/domainbackupxml2xmlout/backup-pull.xml
+++ b/tests/domainbackupxml2xmlout/backup-pull.xml
@@ -6,5 +6,6 @@
       <scratch file='/path/to/file'/>
     </disk>
     <disk name='hda' backup='no'/>
+    <disk name='vdextradisk' backup='no'/>
   </disks>
 </domainbackup>
diff --git a/tests/domainbackupxml2xmlout/backup-push-encrypted.xml b/tests/domainbackupxml2xmlout/backup-push-encrypted.xml
index a955340964..2a5aad93cd 100644
--- a/tests/domainbackupxml2xmlout/backup-push-encrypted.xml
+++ b/tests/domainbackupxml2xmlout/backup-push-encrypted.xml
@@ -25,5 +25,6 @@
         </encryption>
       </target>
     </disk>
+    <disk name='vdextradisk' backup='no'/>
   </disks>
 </domainbackup>
diff --git a/tests/domainbackupxml2xmlout/backup-push-seclabel.xml b/tests/domainbackupxml2xmlout/backup-push-seclabel.xml
index 9986889ba3..59af3e6a6c 100644
--- a/tests/domainbackupxml2xmlout/backup-push-seclabel.xml
+++ b/tests/domainbackupxml2xmlout/backup-push-seclabel.xml
@@ -13,5 +13,6 @@
         <seclabel model='dac' relabel='no'/>
       </target>
     </disk>
+    <disk name='vdextradisk' backup='no'/>
   </disks>
 </domainbackup>
diff --git a/tests/domainbackupxml2xmlout/backup-push.xml b/tests/domainbackupxml2xmlout/backup-push.xml
index 1997c814ae..bc11a93d94 100644
--- a/tests/domainbackupxml2xmlout/backup-push.xml
+++ b/tests/domainbackupxml2xmlout/backup-push.xml
@@ -6,5 +6,6 @@
       <target file='/path/to/file'/>
     </disk>
     <disk name='hda' backup='no'/>
+    <disk name='vdextradisk' backup='no'/>
   </disks>
 </domainbackup>
diff --git a/tests/domainbackupxml2xmlout/empty.xml b/tests/domainbackupxml2xmlout/empty.xml
index b1ba4953be..52d2b4f0af 100644
--- a/tests/domainbackupxml2xmlout/empty.xml
+++ b/tests/domainbackupxml2xmlout/empty.xml
@@ -1 +1,7 @@
-<domainbackup mode='push'/>
+<domainbackup mode='push'>
+  <disks>
+    <disk name='vdextradisk' backup='yes' type='file'>
+      <target file='/fake/vdextradisk.qcow2.SUFFIX'/>
+    </disk>
+  </disks>
+</domainbackup>
diff --git a/tests/genericxml2xmltest.c b/tests/genericxml2xmltest.c
index 2c1e8616dd..8b9b0bafb6 100644
--- a/tests/genericxml2xmltest.c
+++ b/tests/genericxml2xmltest.c
@@ -51,6 +51,23 @@ struct testCompareBackupXMLData {
 };
 
 
+static virDomainDiskDefPtr
+testCompareBackupXMLGetFakeDomdisk(const char *dst)
+{
+    virDomainDiskDefPtr domdisk = NULL;
+
+    if (!(domdisk = virDomainDiskDefNew(NULL)))
+        abort();
+
+    domdisk->dst = g_strdup(dst);
+    domdisk->src->type = VIR_STORAGE_TYPE_FILE;
+    domdisk->src->format = VIR_STORAGE_FILE_QCOW2;
+    domdisk->src->path = g_strdup_printf("/fake/%s.qcow2", dst);
+
+    return domdisk;
+}
+
+
 static int
 testCompareBackupXML(const void *opaque)
 {
@@ -63,6 +80,8 @@ testCompareBackupXML(const void *opaque)
     g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
     g_autofree char *actual = NULL;
     unsigned int parseFlags = 0;
+    g_autoptr(virDomainDef) fakedef = NULL;
+    size_t i;
 
     if (data->internal)
         parseFlags |= VIR_DOMAIN_BACKUP_PARSE_INTERNAL;
@@ -80,6 +99,23 @@ testCompareBackupXML(const void *opaque)
         return -1;
     }
 
+    /* create a fake definition and fill it with disks */
+    if (!(fakedef = virDomainDefNew()))
+        return -1;
+
+    fakedef->ndisks = backup->ndisks + 1;
+    fakedef->disks = g_new0(virDomainDiskDefPtr, fakedef->ndisks);
+
+    for (i = 0; i < backup->ndisks; i++)
+        fakedef->disks[i] = testCompareBackupXMLGetFakeDomdisk(backup->disks[i].name);
+
+    fakedef->disks[fakedef->ndisks -1 ] = testCompareBackupXMLGetFakeDomdisk("vdextradisk");
+
+    if (virDomainBackupAlignDisks(backup, fakedef, "SUFFIX") < 0) {
+        VIR_TEST_VERBOSE("failed to align backup def '%s'", file_in);
+        return -1;
+    }
+
     if (virDomainBackupDefFormat(&buf, backup, data->internal) < 0) {
         VIR_TEST_VERBOSE("failed to format backup def '%s'", file_in);
         return -1;