diff --git a/plugin.php b/plugin.php
index 3d364ce..4d889c3 100644
--- a/plugin.php
+++ b/plugin.php
@@ -17,6 +17,7 @@
 
 require_once __DIR__ . '/simpletoc-admin-settings.php';
 require_once __DIR__ . '/simpletoc-class-headline-ids.php';
+require_once __DIR__ . '/simpletoc-class-headline-ids-wrapper.php';
 
 /**
  * Prevents direct execution of the plugin file.
@@ -166,6 +167,8 @@ function simpletoc_add_ids_to_content( $content ) {
 
 add_filter( 'the_content', __NAMESPACE__ . '\simpletoc_add_ids_to_content', 1 );
 
+
+
 /**
  * Recursively adds IDs to the headings of a nested block structure.
  *
@@ -187,9 +190,9 @@ function add_ids_to_blocks_recursive( $blocks ) {
 	 */
 	$supported_blocks = apply_filters( 'simpletoc_supported_blocks_for_ids', $supported_blocks );
 
-	// Need two separate instances so that IDs aren't double coubnted.
-	$inner_html_id_instance    = new SimpleTOC_Headline_Ids();
-	$inner_content_id_instance = new SimpleTOC_Headline_Ids();
+	// Need two separate instances so that IDs aren't double counted.
+	$inner_html_id_instance    = SimpleTOC_Headline_Ids_Wrapper::get_inner_html_id_instance();
+	$inner_content_id_instance = SimpleTOC_Headline_Ids_Wrapper::get_inner_content_id_instance();
 
 	foreach ( $blocks as &$block ) {
 		if ( isset( $block['blockName'] ) && in_array( $block['blockName'], $supported_blocks, true ) && isset( $block['innerHTML'] ) && isset( $block['innerContent'] ) && isset( $block['innerContent'][0] ) ) {
diff --git a/simpletoc-admin-settings.php b/simpletoc-admin-settings.php
index 692b61e..a59fb8a 100644
--- a/simpletoc-admin-settings.php
+++ b/simpletoc-admin-settings.php
@@ -7,6 +7,11 @@
 
 namespace MToensing\SimpleTOC;
 
+if ( ! defined( 'ABSPATH' ) ) {
+	header( 'Status: 403 Forbidden' );
+	header( 'HTTP/1.1 403 Forbidden' );
+	exit;
+}
 /**
  * Add SimpleTOC global settings page.
  */
diff --git a/simpletoc-class-headline-ids-wrapper.php b/simpletoc-class-headline-ids-wrapper.php
new file mode 100644
index 0000000..37e5676
--- /dev/null
+++ b/simpletoc-class-headline-ids-wrapper.php
@@ -0,0 +1,57 @@
+<?php
+/**
+ * Class to manage headline IDs for the wrapper.
+ *
+ * @package simpletoc
+ */
+
+namespace MToensing\SimpleTOC;
+
+if ( ! defined( 'ABSPATH' ) ) {
+	header( 'Status: 403 Forbidden' );
+	header( 'HTTP/1.1 403 Forbidden' );
+	exit;
+}
+
+/**
+ * Wrapper for the IDs. This ensures that IDs are not double-counted or lost in recursion.
+ */
+class SimpleTOC_Headline_Ids_Wrapper {
+	/**
+	 * The instance of the SimpleTOC_Headline_Ids class for the wrapper.
+	 *
+	 * @var SimpleTOC_Headline_Ids
+	 */
+	private static $inner_content_id_instance = null;
+
+	/**
+	 * The instance of the SimpleTOC_Headline_Ids class for the wrapper.
+	 *
+	 * @var SimpleTOC_Headline_Ids
+	 */
+	private static $inner_html_id_instance = null;
+
+	/**
+	 * Get the instance of the SimpleTOC_Headline_Ids class for the wrapper for inner content.
+	 *
+	 * @return SimpleTOC_Headline_Ids
+	 */
+	public static function get_inner_content_id_instance() {
+		if ( null === self::$inner_content_id_instance ) {
+			self::$inner_content_id_instance = new SimpleTOC_Headline_Ids();
+		}
+		return self::$inner_content_id_instance;
+	}
+
+	/**
+	 * Get the instance of the SimpleTOC_Headline_Ids class for the wrapper for inner HTML.
+	 *
+	 * @return SimpleTOC_Headline_Ids
+	 */
+	public static function get_inner_html_id_instance() {
+		if ( null === self::$inner_html_id_instance ) {
+			self::$inner_html_id_instance = new SimpleTOC_Headline_Ids();
+		}
+		return self::$inner_html_id_instance;
+	}
+}
diff --git a/simpletoc-class-headline-ids.php b/simpletoc-class-headline-ids.php
index 85b95e9..e4b9de5 100644
--- a/simpletoc-class-headline-ids.php
+++ b/simpletoc-class-headline-ids.php
@@ -9,6 +9,12 @@
 
 namespace MToensing\SimpleTOC;
 
+if ( ! defined( 'ABSPATH' ) ) {
+	header( 'Status: 403 Forbidden' );
+	header( 'HTTP/1.1 403 Forbidden' );
+	exit;
+}
+
 /**
  * Class to manage headline IDs.
  *