diff --git a/lib/extension-core.js b/lib/extension-core.js
index 2a6e387f..793679fe 100644
--- a/lib/extension-core.js
+++ b/lib/extension-core.js
@@ -51,7 +51,7 @@ function core(loader) {
   loader.config = function(cfg) {
     for (var c in cfg) {
       var v = cfg[c];
-      if (typeof v == 'object') {
+      if (typeof v == 'object' && !(v instanceof Array)) {
         this[c] = this[c] || {};
         for (var p in v)
           this[c][p] = v[p];