diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1739,7 +1739,9 @@
         if ($is_current_path && $is_current_language) {
           $class[] = 'active';
         }
-        if (isset($link['ajax'])) {
+        // @todo Reconcile Views usage of 'ajax' as a boolean with the rest of
+        //   core's usage of it as an array.
+        if (isset($link['ajax']) && is_array($link['ajax'])) {
           // To attach Ajax behavior, render a link element, rather than just
           // call l().
           $link_element = array(