diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 348dbfe6b1..741f2689f3 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -4068,9 +4068,11 @@
     <attribute name="bus">
       <ref name="usbAddr"/>
     </attribute>
-    <attribute name="port">
-      <ref name="usbPort"/>
-    </attribute>
+    <optional>
+      <attribute name="port">
+        <ref name="usbPort"/>
+      </attribute>
+    </optional>
   </define>
   <define name="spaprvioaddress">
     <optional>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 13a059e21d..44d9857941 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -4839,9 +4839,8 @@ virDomainDeviceInfoFormat(virBufferPtr buf,
         break;
 
     case VIR_DOMAIN_DEVICE_ADDRESS_TYPE_USB:
-        virBufferAsprintf(buf, " bus='%d' port='%s'",
-                          info->addr.usb.bus,
-                          info->addr.usb.port);
+        virBufferAsprintf(buf, " bus='%d'", info->addr.usb.bus);
+        virBufferEscapeString(buf, " port='%s'", info->addr.usb.port);
         break;
 
     case VIR_DOMAIN_DEVICE_ADDRESS_TYPE_SPAPRVIO:
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index fe4bb88f9f..7a3ee81514 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -375,7 +375,8 @@ qemuBuildDeviceAddressStr(virBufferPtr buf,
                                                        VIR_DOMAIN_CONTROLLER_TYPE_USB,
                                                        info->addr.usb.bus)))
             goto cleanup;
-        virBufferAsprintf(buf, ",bus=%s.0,port=%s", contAlias, info->addr.usb.port);
+        virBufferAsprintf(buf, ",bus=%s.0", contAlias);
+        virBufferEscapeString(buf, ",port=%s", info->addr.usb.port);
     } else if (info->type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_SPAPRVIO) {
         if (info->addr.spaprvio.has_reg)
             virBufferAsprintf(buf, ",reg=0x%llx", info->addr.spaprvio.reg);
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-usb-port-missing.args b/tests/qemuxml2argvdata/qemuxml2argv-usb-port-missing.args
new file mode 100644
index 0000000000..3b9d9dfcd1
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-usb-port-missing.args
@@ -0,0 +1,26 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu \
+-name QEMUGuest1 \
+-S \
+-M pc \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefconfig \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-QEMUGuest1/monitor.sock,\
+server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=readline \
+-no-acpi \
+-boot c \
+-usb \
+-device usb-hub,id=hub0,bus=usb.0 \
+-device usb-hub,id=hub1,bus=usb.0 \
+-device usb-mouse,id=input0,bus=usb.0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-usb-port-missing.xml b/tests/qemuxml2argvdata/qemuxml2argv-usb-port-missing.xml
new file mode 100644
index 0000000000..593fcd1e0e
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-usb-port-missing.xml
@@ -0,0 +1,25 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <controller type='usb' index='0'/>
+    <memballoon model='virtio'/>
+    <input type='mouse' bus='usb'>
+      <address type='usb' bus='0'/>
+    </input>
+    <hub type='usb'>
+      <address type='usb' bus='0'/>
+    </hub>
+    <hub type='usb'>
+      <address type='usb' bus='0'/>
+    </hub>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index e0d07e80a6..8abc4b050b 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -1163,6 +1163,9 @@ mymain(void)
     DO_TEST("usb-hub",
             QEMU_CAPS_CHARDEV, QEMU_CAPS_USB_HUB,
             QEMU_CAPS_NODEFCONFIG);
+    DO_TEST("usb-port-missing",
+            QEMU_CAPS_CHARDEV, QEMU_CAPS_USB_HUB,
+            QEMU_CAPS_NODEFCONFIG);
     DO_TEST("usb-ports",
             QEMU_CAPS_CHARDEV, QEMU_CAPS_USB_HUB,
             QEMU_CAPS_NODEFCONFIG);
diff --git a/tests/qemuxml2xmloutdata/qemuxml2xmlout-usb-port-missing.xml b/tests/qemuxml2xmloutdata/qemuxml2xmlout-usb-port-missing.xml
new file mode 100644
index 0000000000..2e29cbdb19
--- /dev/null
+++ b/tests/qemuxml2xmloutdata/qemuxml2xmlout-usb-port-missing.xml
@@ -0,0 +1,36 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <controller type='usb' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='usb'>
+      <address type='usb' bus='0'/>
+    </input>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <hub type='usb'>
+      <address type='usb' bus='0'/>
+    </hub>
+    <hub type='usb'>
+      <address type='usb' bus='0'/>
+    </hub>
+    <memballoon model='virtio'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
+    </memballoon>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2xmltest.c b/tests/qemuxml2xmltest.c
index 86408bf9fa..8a184d271f 100644
--- a/tests/qemuxml2xmltest.c
+++ b/tests/qemuxml2xmltest.c
@@ -591,6 +591,7 @@ mymain(void)
     DO_TEST("interface-server");
     DO_TEST("virtio-lun");
 
+    DO_TEST("usb-port-missing");
     DO_TEST("usb-redir");
     DO_TEST("usb-redir-filter");
     DO_TEST("usb-redir-filter-version");