diff --git a/src/application/views/backend/calendar.php b/src/application/views/backend/calendar.php
index 50821bc8..e936cbca 100644
--- a/src/application/views/backend/calendar.php
+++ b/src/application/views/backend/calendar.php
@@ -244,7 +244,7 @@
                                 </button>
                                 <input type="text" id="filter-existing-customers"
                                        placeholder="<?php echo $this->lang->line('type_to_filter_customers'); ?>"
-                                       style="display: none;" class="input-medium span4"/>
+                                       style="display: none;" class="input-sm"/>
                                 <div id="existing-customers-list" style="display: none;"></div>
                             </legend>