diff --git a/skinStyles/ooui/oojs-ui-toolbars.less b/skinStyles/ooui/oojs-ui-toolbars.less
index 9930d5f2f..a52072b2f 100644
--- a/skinStyles/ooui/oojs-ui-toolbars.less
+++ b/skinStyles/ooui/oojs-ui-toolbars.less
@@ -362,8 +362,8 @@
 }
 
 .oo-ui-menuToolGroup {
-	border-right: 1px solid var( --border-color-base );
-	border-left: 1px solid var( --border-color-base );
+	border-right-color: var( --border-color-base );
+	border-left-color: var( --border-color-base );
 }
 
 .oo-ui-menuToolGroup-tools .oo-ui-tool.oo-ui-widget-enabled:hover {
@@ -385,17 +385,17 @@
 }
 
 .oo-ui-toolbar-position-top > .oo-ui-toolbar-bar {
-	border-bottom: 1px solid var( --border-color-base );
+	border-bottom-color: var( --border-color-base );
 }
 
 .oo-ui-toolbar-position-bottom > .oo-ui-toolbar-bar {
-	border-top: 1px solid var( --border-color-base );
+	border-top-color: var( --border-color-base );
 }
 
 .oo-ui-toolbar-narrow.oo-ui-toolbar-position-top .oo-ui-toolbar-bar::after {
-	border-bottom: 1px solid var( --border-color-base );
+	border-bottom-color: var( --border-color-base );
 }
 
 .oo-ui-toolbar-narrow.oo-ui-toolbar-position-bottom .oo-ui-toolbar-bar::after {
-	border-top: 1px solid var( --border-color-base );
+	border-top-color: var( --border-color-base );
 }