diff --git a/less/button-groups.less b/less/button-groups.less
index ef11cf12aa..6dbb09f4c5 100644
--- a/less/button-groups.less
+++ b/less/button-groups.less
@@ -232,5 +232,5 @@
 [data-toggle="buttons"] > .btn > input[type="checkbox"] {
   position: absolute;
   z-index: -1;
-  opacity: 0;
+  .opacity(0);
 }