diff --git a/lib/ComicBook.js b/lib/ComicBook.js
index b40a8a4..adf9312 100755
--- a/lib/ComicBook.js
+++ b/lib/ComicBook.js
@@ -614,7 +614,7 @@ function ComicBook(id, srcs, opts) {
 
 	ComicBook.prototype.navigation = function (e) {
 
-		var side;
+		var side = false;
 
 		switch (e.type) {
 			case "click":