diff --git a/theme/standard/styles_color.css b/theme/standard/styles_color.css
index 462dcea04b7..07af858e529 100644
--- a/theme/standard/styles_color.css
+++ b/theme/standard/styles_color.css
@@ -1094,3 +1094,8 @@ form.mform .required label {
 form.mform .fdescription.required {
   color:#a00;
 }
+
+/* Accessibility: for Windows High Contrast, partial fix MDL-7493. */
+.sideblock .hide-show a {
+  border:1px solid white;
+}