diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index efc46f991692a51b2d8a164166cadf0974912322..ec64ae01c71fce71c4c1f69d1f13ff53f84a4f8b 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -2614,6 +2614,26 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
                                virDomainNumaGetNodeCount(def->numa));
                 goto cleanup;
             }
+        } else if (cont->type == VIR_DOMAIN_CONTROLLER_TYPE_USB &&
+                   cont->model == -1) {
+            /* Pick a suitable default model for the USB controller if none
+             * has been selected by the user.
+             *
+             * We rely on device availability instead of setting the model
+             * unconditionally because, for some machine types, there's a
+             * chance we will get away with using the legacy USB controller
+             * when the relevant device is not available.
+             *
+             * See qemuBuildControllerDevCommandLine() */
+            if (ARCH_IS_PPC64(def->os.arch)) {
+                /* Default USB controller for ppc64 is pci-ohci */
+                if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_PCI_OHCI))
+                    cont->model = VIR_DOMAIN_CONTROLLER_MODEL_USB_PCI_OHCI;
+            } else {
+                /* Default USB controller for anything else is piix3-uhci */
+                if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_PIIX3_USB_UHCI))
+                    cont->model = VIR_DOMAIN_CONTROLLER_MODEL_USB_PIIX3_UHCI;
+            }
         }
     }
 
diff --git a/tests/qemuxml2xmloutdata/qemuxml2xmlout-ppc64-usb-controller.xml b/tests/qemuxml2xmloutdata/qemuxml2xmlout-ppc64-usb-controller.xml
index 33e78100721ef56753eb85a729a0018835d5b24a..30932e5afd4cf943f10a14aa24927b753c945103 100644
--- a/tests/qemuxml2xmloutdata/qemuxml2xmlout-ppc64-usb-controller.xml
+++ b/tests/qemuxml2xmloutdata/qemuxml2xmlout-ppc64-usb-controller.xml
@@ -19,7 +19,7 @@
   <on_crash>restart</on_crash>
   <devices>
     <emulator>/usr/libexec/qemu-system-ppc64</emulator>
-    <controller type='usb' index='0'>
+    <controller type='usb' index='0' model='pci-ohci'>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
     </controller>
     <controller type='pci' index='0' model='pci-root'/>
diff --git a/tests/qemuxml2xmloutdata/qemuxml2xmlout-usb-controller-default-q35.xml b/tests/qemuxml2xmloutdata/qemuxml2xmlout-usb-controller-default-q35.xml
index 8c4f1f5da27acb68b54ac2b322b0820be79c6e49..082a92e452c50d7ba09d6efccd07a5c663bc5394 100644
--- a/tests/qemuxml2xmloutdata/qemuxml2xmlout-usb-controller-default-q35.xml
+++ b/tests/qemuxml2xmloutdata/qemuxml2xmlout-usb-controller-default-q35.xml
@@ -20,7 +20,7 @@
       <target chassisNr='56'/>
       <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
     </controller>
-    <controller type='usb' index='0'>
+    <controller type='usb' index='0' model='piix3-uhci'>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
     </controller>
     <controller type='sata' index='0'>