diff --git a/assets/styles/root.css b/assets/styles/root.css
index 15c48ad..179eade 100644
--- a/assets/styles/root.css
+++ b/assets/styles/root.css
@@ -180,6 +180,12 @@ details {
   width: 100%;
 }
 
+details:has(#TableOfContents) {
+    box-sizing: border-box;
+    border: 1px solid var(--separator-color);
+    padding: var(--body-item-spacing);
+}
+
 fieldset {
     box-sizing: border-box;
     border: 1px solid var(--separator-color);