diff --git a/lib/core.js b/lib/core.js
index 9102d9b3..345f196d 100644
--- a/lib/core.js
+++ b/lib/core.js
@@ -317,7 +317,7 @@ SystemJSLoader.prototype.config = function(cfg) {
     var hasConfig = false;
     function checkHasConfig(obj) {
       for (var p in obj)
-        if (hasOwnProperty.call(obj, p))
+        if (obj.hasOwnProperty(p))
           return true;
     }
     if (checkHasConfig(loader.packages) || checkHasConfig(loader.meta) || checkHasConfig(loader.depCache) || checkHasConfig(loader.bundles) || checkHasConfig(loader.packageConfigPaths))