diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 5ac4beb2aa..9c4edfac50 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -6967,8 +6967,7 @@ virDomainDiskDefDriverParseXML(virDomainDiskDefPtr def,
     }
 
     if (iotag) {
-        if ((def->iomode = virDomainDiskIoTypeFromString(iotag)) < 0 ||
-            def->iomode == VIR_DOMAIN_DISK_IO_DEFAULT) {
+        if ((def->iomode = virDomainDiskIoTypeFromString(iotag)) <= 0) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                            _("unknown disk io mode '%s'"), iotag);
             goto cleanup;
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 1986f5358d..555d45dc0b 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -622,7 +622,7 @@ typedef enum {
 } virDomainDiskGeometryTrans;
 
 typedef enum {
-    VIR_DOMAIN_DISK_IO_DEFAULT,
+    VIR_DOMAIN_DISK_IO_DEFAULT = 0,
     VIR_DOMAIN_DISK_IO_NATIVE,
     VIR_DOMAIN_DISK_IO_THREADS,