diff --git a/theme/boost/templates/core_grades/edit_tree.mustache b/theme/boost/templates/core_grades/edit_tree.mustache
index 341b5034955..129e286d772 100644
--- a/theme/boost/templates/core_grades/edit_tree.mustache
+++ b/theme/boost/templates/core_grades/edit_tree.mustache
@@ -33,7 +33,7 @@
                 <div class="form-inline mt-3">
                     <input type="hidden" name="bulkmove" value="0" id="bulkmoveinput">
                     <label for="menumoveafter">{{#str}}moveselectedto, grades{{/str}}</label>
-                    <select name="moveafter" id="menumoveafter" class="ignoredirty singleselect select form-control">
+                    <select name="moveafter" id="menumoveafter" class="ignoredirty singleselect custom-select form-control">
                         {{#bulkmoveoptions}}
                             <option value="{{value}}">{{name}}</option>
                         {{/bulkmoveoptions}}