diff --git a/mithril.js b/mithril.js
index d1c77cc8..0736ac4f 100644
--- a/mithril.js
+++ b/mithril.js
@@ -755,7 +755,7 @@ var m = (function app(window, undefined) {
 		else if (isString(root)) {
 			var oldRoute = currentRoute;
 			currentRoute = root;
-			arg1 || {};
+			arg1 = arg1 || {};
 			var queryIndex = currentRoute.indexOf("?");
 			var params = queryIndex > -1 ? parseQueryString(currentRoute.slice(queryIndex + 1)) : {};
 			for (var i in arg1) params[i] = arg1[i];