diff --git a/src/Controller.html b/src/Controller.html
index 4cf9e338..dac8d1ee 100644
--- a/src/Controller.html
+++ b/src/Controller.html
@@ -262,6 +262,7 @@
     position: relative;
     border-radius: 3px;
     cursor: pointer;
+    box-sizing: border-box;
     border-top: solid 4px #fff;
     border-bottom: solid 4px #fff;
   }