diff --git a/nova/tests/unit/virt/libvirt/test_designer.py b/nova/tests/unit/virt/libvirt/test_designer.py
index 7f3323a1a724..f805eb36928a 100644
--- a/nova/tests/unit/virt/libvirt/test_designer.py
+++ b/nova/tests/unit/virt/libvirt/test_designer.py
@@ -205,3 +205,25 @@ class DesignerTestCase(test.NoDBTestCase):
         self.assertEqual('fake-path', conf.vhostuser_path)
         self.assertEqual(512, conf.vhost_rx_queue_size)
         self.assertEqual(1024, conf.vhost_tx_queue_size)
+
+    def test_set_vif_host_backend_vhostuser_config_tx_queue_size(self):
+        conf = config.LibvirtConfigGuestInterface()
+        designer.set_vif_host_backend_vhostuser_config(conf, 'fake-mode',
+                                                       'fake-path', None, 1024)
+        self.assertEqual('vhostuser', conf.net_type)
+        self.assertEqual('unix', conf.vhostuser_type)
+        self.assertEqual('fake-mode', conf.vhostuser_mode)
+        self.assertEqual('fake-path', conf.vhostuser_path)
+        self.assertIsNone(conf.vhost_rx_queue_size)
+        self.assertEqual(1024, conf.vhost_tx_queue_size)
+
+    def test_set_vif_host_backend_vhostuser_config_rx_queue_size(self):
+        conf = config.LibvirtConfigGuestInterface()
+        designer.set_vif_host_backend_vhostuser_config(conf, 'fake-mode',
+                                                       'fake-path', 512, None)
+        self.assertEqual('vhostuser', conf.net_type)
+        self.assertEqual('unix', conf.vhostuser_type)
+        self.assertEqual('fake-mode', conf.vhostuser_mode)
+        self.assertEqual('fake-path', conf.vhostuser_path)
+        self.assertEqual(512, conf.vhost_rx_queue_size)
+        self.assertIsNone(conf.vhost_tx_queue_size)
diff --git a/nova/virt/libvirt/designer.py b/nova/virt/libvirt/designer.py
index 488b9aef89ff..d832fa7aa2a3 100644
--- a/nova/virt/libvirt/designer.py
+++ b/nova/virt/libvirt/designer.py
@@ -166,7 +166,7 @@ def set_vif_host_backend_vhostuser_config(conf, mode, path, rx_queue_size,
     conf.vhostuser_path = path
     if rx_queue_size:
         conf.vhost_rx_queue_size = rx_queue_size
-    if rx_queue_size:
+    if tx_queue_size:
         conf.vhost_tx_queue_size = tx_queue_size