diff --git a/lib/log4js.js b/lib/log4js.js
index 460161c..3785b84 100644
--- a/lib/log4js.js
+++ b/lib/log4js.js
@@ -134,7 +134,7 @@ function addAppender () {
 	args = [ ALL_CATEGORIES ];
     }
     //argument may already be an array
-    if (args[0].forEach) {
+    if (Array.isArray(args[0])) {
 	args = args[0];
     }