diff --git a/src/wp-includes/class-wp-theme.php b/src/wp-includes/class-wp-theme.php
index 3b520782c192..43383dea9eb5 100644
--- a/src/wp-includes/class-wp-theme.php
+++ b/src/wp-includes/class-wp-theme.php
@@ -363,8 +363,7 @@ public function __construct( $theme_dir, $theme_root, $_child = null ) {
 			$theme_path     = $this->theme_root . '/' . $this->stylesheet;
 
 			if (
-				! file_exists( $theme_path . '/templates/index.html' )
-				&& ! file_exists( $theme_path . '/block-templates/index.html' ) // Deprecated path support since 5.9.0.
+				! $this->is_block_theme()
 				&& ! file_exists( $theme_path . '/index.php' )
 			) {
 				$error_message = sprintf(
@@ -380,7 +379,7 @@ public function __construct( $theme_dir, $theme_root, $_child = null ) {
 				$this->cache_add(
 					'theme',
 					array(
-						'block_theme' => $this->is_block_theme(),
+						'block_theme' => $this->block_theme,
 						'headers'     => $this->headers,
 						'errors'      => $this->errors,
 						'stylesheet'  => $this->stylesheet,