diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index c28c76ff13298c571761d97d46f1fb49bfb72a3e..d924ddbdce065bb2eeec2c1fdb1f65a204b17817 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -14806,9 +14806,13 @@ qemuDomainGetBlockIoTune(virDomainPtr dom,
     }
 
     if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
-        int idx = virDomainDiskIndexByName(vm->def, disk, true);
-        if (idx < 0)
+        int idx = virDomainDiskIndexByName(persistentDef, disk, true);
+        if (idx < 0) {
+            virReportError(VIR_ERR_INVALID_ARG,
+                           _("disk '%s' was not found in the domain config"),
+                           disk);
             goto endjob;
+        }
         reply = persistentDef->disks[idx]->blkdeviotune;
     }