diff --git a/booking.js b/booking.js
index bcb1552..68a4d4b 100644
--- a/booking.js
+++ b/booking.js
@@ -6,7 +6,8 @@ Drupal.ajax.prototype.commands.bookingEmailIDs =  function(ajax, response, statu
     jQuery(function($) {
         var arr = $.parseJSON($('input#booking_email_default_ids').val())
         $('#booking-manual-email-form').find(':checkbox[name^="table"]').each(function () {
-            $(this).prop("checked", ($.inArray($(this).val(), arr) != -1));
+            //.prop() doesn't exist in Drupal's old version of jQuery so use .attr() instead
+            $(this).attr("checked", ($.inArray($(this).val(), arr) != -1));
         });  
         alert(arr[0]);                
     });