diff --git a/application/views/components/booking_time_step.php b/application/views/components/booking_time_step.php
index 4689aafe..def25503 100644
--- a/application/views/components/booking_time_step.php
+++ b/application/views/components/booking_time_step.php
@@ -25,7 +25,7 @@
                             <?= lang('timezone') ?>
                         </label>
                         <?php component('timezone_dropdown', [
-                            'attributes' => 'id="select-timezone" class="form-control" value="UTC"',
+                            'attributes' => 'id="select-timezone" class="form-select" value="UTC"',
                             'grouped_timezones' => $grouped_timezones,
                         ]); ?>
                     </div>
diff --git a/application/views/pages/calendar.php b/application/views/pages/calendar.php
index 1b9d8bbf..83c90d70 100755
--- a/application/views/pages/calendar.php
+++ b/application/views/pages/calendar.php
@@ -7,7 +7,7 @@
         <div id="calendar-filter" class="col-md-3">
             <div class="calendar-filter-items">
                 <select id="select-filter-item"
-                        class="form-control col"
+                        class="form-select col"
                         data-tippy-content="<?= lang('select_filter_item_hint') ?>"
                         aria-label="Filter">
                     <!-- JS -->
diff --git a/assets/css/general.scss b/assets/css/general.scss
index 29778f84..14410542 100644
--- a/assets/css/general.scss
+++ b/assets/css/general.scss
@@ -427,7 +427,8 @@ body .popover-body a {
     color: #dc3545;
 }
 
-.has-error .form-control {
+.has-error .form-control,
+.has-error .form-select {
     border-color: #dc3545;
 }
 
diff --git a/assets/css/layouts/backend_layout.scss b/assets/css/layouts/backend_layout.scss
index 25051b50..961beec9 100644
--- a/assets/css/layouts/backend_layout.scss
+++ b/assets/css/layouts/backend_layout.scss
@@ -196,7 +196,9 @@ body legend {
 }
 
 .backend-page .form-control:disabled,
-.backend-page .form-control[readonly] {
+.backend-page .form-control[readonly],
+.backend-page .form-select:disabled,
+.backend-page .form-select[readonly] {
     background-color: #fff;
     color: #666;
     border-color: #fff;
@@ -610,7 +612,8 @@ body .form-horizontal .controls {
         text-align: right;
     }
 
-    #calendar-page #calendar-filter .form-group .form-control {
+    #calendar-page #calendar-filter .form-group .form-control,
+    #calendar-page #calendar-filter .form-group .form-select {
         max-width: 300px;
         margin-bottom: 0;
     }
@@ -845,7 +848,8 @@ body .form-horizontal .controls {
 #working-plan-exceptions-breaks {
     table-layout: fixed;
 
-    .form-control {
+    .form-control,
+    .form-select {
         width: 100% !important;
     }
 }
@@ -997,7 +1001,8 @@ body .form-horizontal .controls {
     margin-left: 12px;
 }
 
-#booking-settings-page .fields-row .form-control {
+#booking-settings-page .fields-row .form-control,
+#booking-settings-page .fields-row .form-select {
     border: 1px dashed #999 !important;
 }