diff --git a/gui/default/assets/css/overrides.css b/gui/default/assets/css/overrides.css
index e449ab879..c79f9ab22 100644
--- a/gui/default/assets/css/overrides.css
+++ b/gui/default/assets/css/overrides.css
@@ -437,3 +437,9 @@ ul.three-columns li, ul.two-columns li {
 .form-horizontal {
     margin-bottom: 10px;
 }
+
+/* Use the same style as Bootstrap uses for disabled <select>. */
+.form-control option[disabled] {
+    background-color: #eeeeee;
+    opacity: 1;
+}