diff --git a/src/components/tree/Headings.astro b/src/components/tree/Headings.astro
index b374b13..b77220f 100644
--- a/src/components/tree/Headings.astro
+++ b/src/components/tree/Headings.astro
@@ -8,6 +8,27 @@ interface Props {
   headings: MarkdownHeading[];
 }
 
+export type Nested = MarkdownHeading & { children?: MarkdownHeading[] };
+
+
+function fold(headings: MarkdownHeading[]): Nested[] {
+  const toc = [] as Nested[];
+  const map = new Map<number, Nested>();
+  for (const h of headings) {
+    const heading = { ...h };
+    map.set(heading.depth, heading);
+    if (heading.depth === 2)
+      toc.push(heading)
+    else {
+      const backref = map.get(heading.depth - 1)!;
+      backref.children
+        ? backref.children.push(heading)
+        : backref.children = [heading];
+    }
+  }
+  return toc;
+}
+
 
 const { headings } = Astro.props;
 ---
@@ -16,5 +37,7 @@ const { headings } = Astro.props;
   <span class="link-tree__heading-text">Content</span>
 </h2>
 <nav id="table-of-contents" class="link-tree__nav">
-  <HeadingsList headings={Maybe.of(headings)} />
+  <HeadingsList
+    headings={Maybe.of(headings).map(fold)}
+  />
 </nav>
diff --git a/src/components/tree/HeadingsList.astro b/src/components/tree/HeadingsList.astro
index 26f2bbe..c7efdf5 100644
--- a/src/components/tree/HeadingsList.astro
+++ b/src/components/tree/HeadingsList.astro
@@ -1,38 +1,17 @@
 ---
-import type { MarkdownHeading } from 'astro';
 import { Maybe } from 'purify-ts';
+import type { Nested } from './Headings.astro';
 
 
 interface Props {
-  headings: Maybe<MarkdownHeading[]>;
+  headings: Maybe<Nested[]>;
 }
 
-type Nested = MarkdownHeading & { children?: MarkdownHeading[] };
-
 
 const { headings } = Astro.props;
-
-function fold(headings: MarkdownHeading[]) {
-  const toc = [] as Nested[];
-  const map = new Map<number, Nested>();
-  for (const h of headings) {
-    const heading = { ...h };
-    map.set(heading.depth, heading);
-    if (heading.depth === 2)
-      toc.push(heading)
-    else {
-      const backref = map.get(heading.depth - 1)!;
-      backref.children
-        ? backref.children.push(heading)
-        : backref.children = [heading];
-    }
-  }
-  return toc;
-}
 ---
 
 {headings
-  .map(fold)
   .map(headings => 
     <ul class="link-tree__nav-list">
       {headings.map(heading =>