diff --git a/lib/compat/wordpress-6.1/script-loader.php b/lib/compat/wordpress-6.1/script-loader.php
index 4948882c113a88..d554dbf7faf04a 100644
--- a/lib/compat/wordpress-6.1/script-loader.php
+++ b/lib/compat/wordpress-6.1/script-loader.php
@@ -86,7 +86,7 @@ function gutenberg_enqueue_global_styles() {
  * This is needed for backwards compatibility for button blocks specifically.
  */
 function gutenberg_enqueue_classic_theme_styles() {
-	if ( ! wp_is_block_theme() ) {
+	if ( ! WP_Theme_JSON_Resolver::theme_has_support() ) {
 		wp_register_style( 'classic-theme-styles', gutenberg_url( 'build/block-library/classic.css' ), array(), true );
 		wp_enqueue_style( 'classic-theme-styles' );
 	}
@@ -104,7 +104,7 @@ function gutenberg_enqueue_classic_theme_styles() {
  * @return array A filtered array of editor settings.
  */
 function gutenberg_add_editor_classic_theme_styles( $editor_settings ) {
-	if ( wp_is_block_theme() ) {
+	if ( WP_Theme_JSON_Resolver::theme_has_support() ) {
 		return $editor_settings;
 	}
 
@@ -113,13 +113,15 @@ function gutenberg_add_editor_classic_theme_styles( $editor_settings ) {
 	// This follows the pattern of get_block_editor_theme_styles,
 	// but we can't use get_block_editor_theme_styles directly as it
 	// only handles external files or theme files.
-	$editor_settings['styles'][] = array(
+	$classic_theme_styles_settings = array(
 		'css'            => file_get_contents( $classic_theme_styles ),
-		'baseURL'        => get_theme_file_uri( $classic_theme_styles ),
-		'__unstableType' => 'theme',
+		'__unstableType' => 'core',
 		'isGlobalStyles' => false,
 	);
 
+	// Add these settings to the start of the array so that themes can override them.
+	array_unshift( $editor_settings['styles'], $classic_theme_styles_settings );
+
 	return $editor_settings;
 }
 add_filter( 'block_editor_settings_all', 'gutenberg_add_editor_classic_theme_styles' );