diff --git a/src/_assets/css/base.css b/src/_assets/css/base.css
index d5574f8..09a6ef5 100644
--- a/src/_assets/css/base.css
+++ b/src/_assets/css/base.css
@@ -128,6 +128,10 @@ table {
   width: 100%;
 }
 
+thead {
+  border-block-end: calc(0.5 * var(--step)) solid var(--color-fg);
+}
+
 th, td {
   text-align: start;
   border-block-end: calc(0.25 * var(--step)) solid;