diff --git a/term_reference_tree.js b/term_reference_tree.js
index aa6605f..0fcf82e 100644
--- a/term_reference_tree.js
+++ b/term_reference_tree.js
@@ -2,7 +2,7 @@
   Drupal.behaviors.termReferenceTree = {
     attach: function(context, settings) {
       // Bind the term expand/contract button to slide toggle the list underneath.
-      $('.term-reference-tree-button', context).click(function() {
+      $('.term-reference-tree-button', context).once('term-reference-tree-button').click(function() {
         $(this).toggleClass('term-reference-tree-collapsed');
         $(this).siblings('ul').slideToggle('fast');
       });
@@ -15,7 +15,7 @@
       */
 
 
-      $('.term-reference-tree', context).each(function() {
+      $('.term-reference-tree', context).once('term-reference-tree', function() {
         // On page load, check whether the maximum number of choices is already selected.
         // If so, disable the other options.
         var tree = $(this);