diff --git a/includes/jquery.drilldown.js b/includes/jquery.drilldown.js
index 5e085fb..ae18fbc 100644
--- a/includes/jquery.drilldown.js
+++ b/includes/jquery.drilldown.js
@@ -83,10 +83,11 @@
             if (breadcrumb[key]) {
               // We don't use the $().clone() method here because of an
               // IE & jQuery 1.2 bug.
-              var clone = $('<a></a>')
-                .attr('href', $(breadcrumb[key]).attr('href'))
-                .attr('class', $(breadcrumb[key]).attr('class'))
-                .html($(breadcrumb[key]).html())
+              var clone = $('<a></a>');
+              // attr() may return undefined since jquery 1.6
+              clone.attr('href', $(breadcrumb[key]).attr('href'));
+              clone.attr('class', $(breadcrumb[key]).attr('class'));
+              clone.html($(breadcrumb[key]).html())
                 .addClass('depth-'+key)
                 .appendTo(trail);