diff --git a/scss/_custom-forms.scss b/scss/_custom-forms.scss
index a73359c86c..39f164822c 100644
--- a/scss/_custom-forms.scss
+++ b/scss/_custom-forms.scss
@@ -135,7 +135,7 @@
 .custom-select {
   display: inline-block;
   max-width: 100%;
-  $select-border-width: ($border-width * 2);
+  $select-border-width: ($custom-select-border-width * 2);
   height: calc(#{$input-height} + #{$select-border-width});
   padding: $custom-select-padding-y ($custom-select-padding-x + $custom-select-indicator-padding) $custom-select-padding-y $custom-select-padding-x;
   line-height: $custom-select-line-height;