diff --git a/osm_openvim/httpserver.py b/osm_openvim/httpserver.py
index edf1e8d..17925ac 100644
--- a/osm_openvim/httpserver.py
+++ b/osm_openvim/httpserver.py
@@ -1831,7 +1831,9 @@
             delete_dhcp_ovs_bridge(vlan, net_id)
             delete_mac_dhcp(vm_ip, vlan, mac)
             config_dic['host_threads'][server['host_id']].insert_task('del-ovs-port', vlan, net_id)
-    return format_out(data + warn_text)
+    if warn_text:
+        data["result"] += warn_text
+    return format_out(data)