diff --git a/js/openseadragon_viewer.js b/js/openseadragon_viewer.js
index f6d6fb0..7883887 100644
--- a/js/openseadragon_viewer.js
+++ b/js/openseadragon_viewer.js
@@ -124,5 +124,6 @@
             });
         }
 
+        return viewer;
     };
 })(once);