diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 3c0342e17a..fd23c4627e 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -397,12 +397,15 @@ static int peer_detach(VirtIONet *n, int index)
 static void virtio_net_set_queues(VirtIONet *n)
 {
     int i;
+    int r;
 
     for (i = 0; i < n->max_queues; i++) {
         if (i < n->curr_queues) {
-            assert(!peer_attach(n, i));
+            r = peer_attach(n, i);
+            assert(!r);
         } else {
-            assert(!peer_detach(n, i));
+            r = peer_detach(n, i);
+            assert(!r);
         }
     }
 }