diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 349fc28c2a..01b7187637 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -8784,6 +8784,12 @@ virDomainDiskDefMirrorParse(virDomainDiskDefPtr def,
         return -1;
     }
 
+    if (virParseScaledValue("./format/metadata_cache/max_size", NULL,
+                            ctxt,
+                            &def->mirror->metadataCacheMaxSize,
+                            1, ULLONG_MAX, false) < 0)
+        return -1;
+
     return 0;
 }
 
@@ -24283,6 +24289,8 @@ virDomainDiskDefFormatMirror(virBufferPtr buf,
 {
     g_auto(virBuffer) attrBuf = VIR_BUFFER_INITIALIZER;
     g_auto(virBuffer) childBuf = VIR_BUFFER_INIT_CHILD(buf);
+    g_auto(virBuffer) formatAttrBuf = VIR_BUFFER_INITIALIZER;
+    g_auto(virBuffer) formatChildBuf = VIR_BUFFER_INIT_CHILD(&childBuf);
     const char *formatStr = NULL;
 
     /* For now, mirroring is currently output-only: we only output it
@@ -24311,7 +24319,19 @@ virDomainDiskDefFormatMirror(virBufferPtr buf,
         virBufferEscapeString(&attrBuf, " ready='%s'",
                               virDomainDiskMirrorStateTypeToString(disk->mirrorState));
 
-    virBufferEscapeString(&childBuf, "<format type='%s'/>\n", formatStr);
+    virBufferEscapeString(&formatAttrBuf, " type='%s'", formatStr);
+    if (disk->mirror->metadataCacheMaxSize > 0) {
+        g_auto(virBuffer) metadataCacheChildBuf = VIR_BUFFER_INIT_CHILD(&formatChildBuf);
+
+        virBufferAsprintf(&metadataCacheChildBuf,
+                          "<max_size unit='bytes'>%llu</max_size>\n",
+                          disk->mirror->metadataCacheMaxSize);
+
+        virXMLFormatElement(&formatChildBuf, "metadata_cache", NULL, &metadataCacheChildBuf);
+    }
+
+    virXMLFormatElement(&childBuf, "format", &formatAttrBuf, &formatChildBuf);
+
     if (virDomainDiskSourceFormat(&childBuf, disk->mirror, "source", 0, true,
                                   flags, false, false, xmlopt) < 0)
         return -1;
diff --git a/tests/qemuxml2argvdata/disk-mirror.xml b/tests/qemuxml2argvdata/disk-mirror.xml
index 2d61fe29c3..73886e99f4 100644
--- a/tests/qemuxml2argvdata/disk-mirror.xml
+++ b/tests/qemuxml2argvdata/disk-mirror.xml
@@ -54,6 +54,20 @@
       </mirror>
       <target dev='vdb' bus='virtio'/>
     </disk>
+    <disk type='file' device='disk'>
+      <source file='/tmp/data2.img'/>
+      <backingStore/>
+      <mirror type='file' file='/tmp/copy2.img' format='qcow2' job='copy'>
+        <format type='qcow2'>
+          <metadata_cache>
+            <max_size unit='bytes'>1234</max_size>
+          </metadata_cache>
+        </format>
+        <source file='/tmp/copy2.img'/>
+        <backingStore/>
+      </mirror>
+      <target dev='vdc' bus='virtio'/>
+    </disk>
     <controller type='usb' index='0'/>
     <controller type='ide' index='0'/>
     <controller type='pci' index='0' model='pci-root'/>
diff --git a/tests/qemuxml2xmloutdata/disk-mirror-active.xml b/tests/qemuxml2xmloutdata/disk-mirror-active.xml
index 17fb061d49..0e2669398c 100644
--- a/tests/qemuxml2xmloutdata/disk-mirror-active.xml
+++ b/tests/qemuxml2xmloutdata/disk-mirror-active.xml
@@ -61,6 +61,22 @@
       <target dev='vdb' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
     </disk>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source file='/tmp/data2.img'/>
+      <backingStore/>
+      <mirror type='file' file='/tmp/copy2.img' format='qcow2' job='copy'>
+        <format type='qcow2'>
+          <metadata_cache>
+            <max_size unit='bytes'>1234</max_size>
+          </metadata_cache>
+        </format>
+        <source file='/tmp/copy2.img'/>
+        <backingStore/>
+      </mirror>
+      <target dev='vdc' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+    </disk>
     <controller type='usb' index='0'>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
     </controller>
@@ -71,7 +87,7 @@
     <input type='mouse' bus='ps2'/>
     <input type='keyboard' bus='ps2'/>
     <memballoon model='virtio'>
-      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
     </memballoon>
   </devices>
 </domain>
diff --git a/tests/qemuxml2xmloutdata/disk-mirror-inactive.xml b/tests/qemuxml2xmloutdata/disk-mirror-inactive.xml
index 157ffcf6b2..6c7f92c1cc 100644
--- a/tests/qemuxml2xmloutdata/disk-mirror-inactive.xml
+++ b/tests/qemuxml2xmloutdata/disk-mirror-inactive.xml
@@ -43,6 +43,13 @@
       <target dev='vdb' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
     </disk>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source file='/tmp/data2.img'/>
+      <backingStore/>
+      <target dev='vdc' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+    </disk>
     <controller type='usb' index='0'>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
     </controller>
@@ -53,7 +60,7 @@
     <input type='mouse' bus='ps2'/>
     <input type='keyboard' bus='ps2'/>
     <memballoon model='virtio'>
-      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
     </memballoon>
   </devices>
 </domain>