diff --git a/src/wp-includes/class-wp-theme.php b/src/wp-includes/class-wp-theme.php
index 3b520782c1..bd16abd16b 100644
--- a/src/wp-includes/class-wp-theme.php
+++ b/src/wp-includes/class-wp-theme.php
@@ -360,12 +360,10 @@ final class WP_Theme implements ArrayAccess {
 
 		if ( ! $this->template ) {
 			$this->template = $this->stylesheet;
-			$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.
-				&& ! file_exists( $theme_path . '/index.php' )
+				! $this->is_block_theme()
+				&& ! file_exists( $this->theme_root . '/' . $this->stylesheet . '/index.php' )
 			) {
 				$error_message = sprintf(
 					/* translators: 1: templates/index.html, 2: index.php, 3: Documentation URL, 4: Template, 5: style.css */