diff --git a/views/style.erb b/views/style.erb
index 9496873..b0577cb 100644
--- a/views/style.erb
+++ b/views/style.erb
@@ -21,4 +21,8 @@
     background-color: <%= v[:color] %> !important;
   }
 
+  .mj-cell-<%= v[:id] %>:hover {
+    border-left-width: 1px;
+    border-right-width: 1px;
+  }
 <% end %>