diff --git a/addons/web/static/tests/helpers/mock_server.js b/addons/web/static/tests/helpers/mock_server.js
index 98e5289cf21..cab291ec012 100644
--- a/addons/web/static/tests/helpers/mock_server.js
+++ b/addons/web/static/tests/helpers/mock_server.js
@@ -94,6 +94,7 @@ var MockServer = Class.extend({
         args = JSON.parse(JSON.stringify(args));
         if (logLevel === 2) {
             console.log('%c[rpc] request ' + route, 'color: blue; font-weight: bold;', args);
+            args = JSON.parse(JSON.stringify(args));
         }
         return this._performRpc(route, args).then(function (result) {
             var resultString = JSON.stringify(result || false);