diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index f99e363507..7b0879d5cc 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4145,16 +4145,8 @@ qemuBuildDriveStr(virConnectPtr conn,
 
 static bool
 qemuCheckIOThreads(virDomainDefPtr def,
-                   virQEMUCapsPtr qemuCaps,
                    virDomainDiskDefPtr disk)
 {
-    /* Have capability */
-    if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_IOTHREAD)) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                       _("IOThreads not supported for this QEMU"));
-        return false;
-    }
-
     /* Right "type" of disk" */
     if (disk->bus != VIR_DOMAIN_DISK_BUS_VIRTIO ||
         (disk->info.type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI &&
@@ -4208,7 +4200,7 @@ qemuBuildDriveDevStr(virDomainDefPtr def,
     if (!qemuCheckCCWS390AddressSupport(def, disk->info, qemuCaps, disk->dst))
         goto error;
 
-    if (disk->iothread && !qemuCheckIOThreads(def, qemuCaps, disk))
+    if (disk->iothread && !qemuCheckIOThreads(def, disk))
         goto error;
 
     switch (disk->bus) {
@@ -9462,8 +9454,13 @@ qemuBuildCommandLine(virConnectPtr conn,
     virCommandAddArg(cmd, smp);
     VIR_FREE(smp);
 
-    if (def->niothreadids > 0 &&
-        virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_IOTHREAD)) {
+    if (def->niothreadids) {
+        if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_IOTHREAD)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("IOThreads not supported for this QEMU"));
+            goto error;
+        }
+
         /* Create iothread objects using the defined iothreadids list
          * and the defined id and name from the list. These may be used
          * by a disk definition which will associate to an iothread by
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index e31885b37e..07e41f0cda 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -2296,8 +2296,32 @@ qemuProcessDetectIOThreadPIDs(virQEMUDriverPtr driver,
     int ret = -1;
     size_t i;
 
-    if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_OBJECT_IOTHREAD))
+    if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_OBJECT_IOTHREAD)) {
+        /* The following check is because at one time a domain could
+         * define iothreadids and start the domain - only failing the
+         * capability check when attempting to add a disk. Because the
+         * iothreads and [n]iothreadids were left untouched other code
+         * assumed it could use the ->thread_id value to make thread_id
+         * based adjustments (e.g. pinning, scheduling) which while
+         * succeeding would execute on the calling thread.
+         */
+        if (vm->def->niothreadids) {
+            for (i = 0; i < vm->def->niothreadids; i++) {
+                /* Check if the domain had defined any iothreadid elements
+                 * and supply a VIR_INFO indicating that it's being removed.
+                 */
+                if (!vm->def->iothreadids[i]->autofill)
+                    VIR_INFO("IOThreads not supported, remove iothread id '%u'",
+                             vm->def->iothreadids[i]->iothread_id);
+                virDomainIOThreadIDDefFree(vm->def->iothreadids[i]);
+            }
+            /* Remove any trace */
+            VIR_FREE(vm->def->iothreadids);
+            vm->def->niothreadids = 0;
+            vm->def->iothreads = 0;
+        }
         return 0;
+    }
 
     /* Get the list of IOThreads from qemu */
     if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cputune-numatune.args b/tests/qemuxml2argvdata/qemuxml2argv-cputune-numatune.args
index 481f72ffd2..affe648089 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-cputune-numatune.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-cputune-numatune.args
@@ -1,5 +1,6 @@
 LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
 /usr/bin/qemu-system-x86_64 -S -M pc-q35-2.3 -m 128 \
 -smp 2,maxcpus=6,sockets=6,cores=1,threads=1 \
+-object iothread,id=iothread1 -object iothread,id=iothread2 \
 -nographic -monitor unix:/tmp/test-monitor,server,nowait -no-acpi \
 -boot c -net none -serial none -parallel none
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-iothreads-nocap.xml b/tests/qemuxml2argvdata/qemuxml2argv-iothreads-nocap.xml
new file mode 100644
index 0000000000..61871e7b6c
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-iothreads-nocap.xml
@@ -0,0 +1,37 @@
+<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'>2</vcpu>
+  <iothreads>4</iothreads>
+  <iothreadids>
+    <iothread id='5'/>
+    <iothread id='6'/>
+  </iothreadids>
+  <cputune>
+    <iothreadpin iothread='5' cpuset='2'/>
+    <iothreadpin iothread='6' cpuset='1'/>
+  </cputune>
+  <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>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='none'/>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index 80cb55ec3e..53580e3d68 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -1285,6 +1285,7 @@ mymain(void)
     DO_TEST("iothreads", QEMU_CAPS_OBJECT_IOTHREAD);
     DO_TEST("iothreads-ids", QEMU_CAPS_OBJECT_IOTHREAD);
     DO_TEST("iothreads-ids-partial", QEMU_CAPS_OBJECT_IOTHREAD);
+    DO_TEST_FAILURE("iothreads-nocap", NONE);
     DO_TEST("iothreads-disk", QEMU_CAPS_OBJECT_IOTHREAD, QEMU_CAPS_DEVICE,
             QEMU_CAPS_DRIVE);
     DO_TEST("iothreads-disk-virtio-ccw", QEMU_CAPS_OBJECT_IOTHREAD, QEMU_CAPS_DEVICE,
@@ -1338,6 +1339,7 @@ mymain(void)
     DO_TEST_PARSE_ERROR("cputune-vcpusched-overlap", QEMU_CAPS_NAME);
     DO_TEST("cputune-numatune", QEMU_CAPS_SMP_TOPOLOGY,
             QEMU_CAPS_KVM,
+            QEMU_CAPS_OBJECT_IOTHREAD,
             QEMU_CAPS_OBJECT_MEMORY_RAM,
             QEMU_CAPS_OBJECT_MEMORY_FILE);