diff --git a/lib/compat/wordpress-5.9/block-template-utils.php b/lib/compat/wordpress-5.9/block-template-utils.php
index 690fae6a16a464..4e9d5c7680e575 100644
--- a/lib/compat/wordpress-5.9/block-template-utils.php
+++ b/lib/compat/wordpress-5.9/block-template-utils.php
@@ -37,7 +37,11 @@ function get_block_theme_folders( $theme_stylesheet = null ) {
 		$root_dir   = get_theme_root( $theme_name );
 		$theme_dir  = "$root_dir/$theme_name";
 
-		if ( is_readable( $theme_dir . '/block-templates/index.html' ) ) {
+		$parent_theme_name = get_template();
+		$parent_root_dir   = get_theme_root( $parent_theme_name );
+		$parent_theme_dir  = "$parent_root_dir/$parent_theme_name";
+
+		if ( is_readable( $theme_dir . '/block-templates/index.html' ) || is_readable( $parent_theme_dir . '/block-templates/index.html' ) ) {
 			return array(
 				'wp_template'      => 'block-templates',
 				'wp_template_part' => 'block-template-parts',