diff --git a/browser/themes/shared/customizableui/customizeMode.inc.css b/browser/themes/shared/customizableui/customizeMode.inc.css
index 7e283728dab1..154d604f0473 100644
--- a/browser/themes/shared/customizableui/customizeMode.inc.css
+++ b/browser/themes/shared/customizableui/customizeMode.inc.css
@@ -57,6 +57,7 @@
 
 .customizationmode-button {
   border: 1px solid #b1b1b1;
+  border-radius: 2px;
   background-color: #fcfcfd;
   -moz-appearance: none;
 }