diff --git a/src/Bundle.js b/src/Bundle.js
index e5d9090..00d68d9 100644
--- a/src/Bundle.js
+++ b/src/Bundle.js
@@ -79,6 +79,8 @@ Bundle.prototype = {
 	},
 
 	generateMap ( options ) {
+		options = options || {};
+
 		let offsets = {};
 
 		let names = [];