diff --git a/attachment_preview/static/src/js/attachment_preview.js b/attachment_preview/static/src/js/attachment_preview.js
index d75e9922..f47426d3 100644
--- a/attachment_preview/static/src/js/attachment_preview.js
+++ b/attachment_preview/static/src/js/attachment_preview.js
@@ -27,10 +27,11 @@ openerp.attachment_preview = function(instance)
             attachment_title)
     {
         var url = (window.location.origin || '') +
-            '/attachment_preview/static/lib/ViewerJS/index.html#' +
+            '/attachment_preview/static/lib/ViewerJS/index.html' +
+            '&type=' + encodeURIComponent(attachment_extension) +
+            '#' +
             attachment_url.replace(window.location.origin, '') +
             '&title=' + encodeURIComponent(attachment_title) +
-            '&ext=.' + encodeURIComponent(attachment_extension);
         window.open(url);
     };
     openerp.attachment_preview.can_preview = function(extension)
diff --git a/attachment_preview/static/src/js/viewerjs_tweaks.js b/attachment_preview/static/src/js/viewerjs_tweaks.js
index 197aba59..2eb1968f 100644
--- a/attachment_preview/static/src/js/viewerjs_tweaks.js
+++ b/attachment_preview/static/src/js/viewerjs_tweaks.js
@@ -24,6 +24,10 @@
 var original_Viewer = Viewer;
 Viewer = function(plugin, parameters)
 {
+    if(!plugin)
+    {
+        alert('Unsupported file type');
+    }
     var matches = (/&title=([^&]+)&/).exec(window.location.hash);
     if(matches && matches.length > 1)
     {