diff --git a/plone/portlet/collection/collection.pt b/plone/portlet/collection/collection.pt
index dde1bf5..1d74e3d 100644
--- a/plone/portlet/collection/collection.pt
+++ b/plone/portlet/collection/collection.pt
@@ -40,7 +40,7 @@
                                  src python:view.getMimeTypeIcon(obj);"> 
 
             <img tal:condition="python: obj.getIcon and thumb_scale and not supress_thumb"
-                 tal:replace="structure python:image_scale.tag(obj, 'image', scale=thumb_scale, css_class='pull-right image-'+thumb_scale)" />
+                 tal:replace="structure python:image_scale.tag(obj, 'image', scale=thumb_scale, css_class='pull-right thumb-'+thumb_scale)" />
 
             <span tal:replace="obj/Title">
              Title </span>