diff --git a/packages/theme-default/src/step.css b/packages/theme-default/src/step.css
index 45c549b02..dc1d43313 100644
--- a/packages/theme-default/src/step.css
+++ b/packages/theme-default/src/step.css
@@ -59,6 +59,7 @@
       border-style: solid;
       border-color: inherit;
       transition: all 150ms;
+      box-sizing: border-box;
       width: 0;
       height: 0;
     }