diff --git a/includes/utilities.php b/includes/utilities.php
index 5867914..49e090d 100644
--- a/includes/utilities.php
+++ b/includes/utilities.php
@@ -196,8 +196,8 @@ function build_page_chapter_index($blocks)
 		if ($block['blockName'] == 'homegrade-content-blocks/content-heading'  && isset($block['attrs']['title']) && isset($block['attrs']['headingLevel']) && $block['attrs']['headingLevel'] == "h2") {
 			array_push($chapterBlockIndex, [
 				'block-type' =>  $block['blockName'],
-				'anchor' => 	"#" . strip_tags($block['attrs']['idName']),
-				'title' => strip_tags($block['attrs']['title']),
+				'anchor' => 	"#" . preg_replace('/[^a-zA-Z0-9]/', '',  strip_tags($block['attrs']['idName'])), // remove html tags all non-alphanumeric characters
+				'title' => preg_replace('/[^a-zA-Z0-9\s]/', '', strip_tags($block['attrs']['title'])), // remove html tags all non-alphanumeric characters
 			]);
 		}
 		if ($block['blockName'] == 'homegrade-content-blocks/chapitrage-thematique') {