diff --git a/customize.html b/customize.html
index 9e46798e..82b712de 100644
--- a/customize.html
+++ b/customize.html
@@ -509,14 +509,11 @@ base_url: "../"
     </div>
 
     <div class="row">
-<!--
-  Temporarily removed until mixins are restored in v3.1
       <div class="col-xs-6 col-sm-4">
         <label>@grid-columns</label>
         <input type="text" class="form-control" placeholder="12" data-var="@grid-columns">
         <p class="help-block">Number of columns in the grid.</p>
       </div>
- -->
       <div class="col-xs-6 col-sm-4">
         <label>@grid-gutter-width</label>
         <input type="text" class="form-control" placeholder="30px" data-var="@grid-gutter-width">