diff --git a/src/theme/book.css b/src/theme/book.css
index 3646bc65d0..aacfea8407 100644
--- a/src/theme/book.css
+++ b/src/theme/book.css
@@ -163,7 +163,7 @@ table thead td {
 }
 .menu-bar i {
   position: relative;
-  margin: 0 10px;
+  padding: 0 10px;
   z-index: 10;
   line-height: 50px;
   -webkit-transition: color 0.5s;