diff --git a/lib/class-wp-theme-json-resolver-gutenberg.php b/lib/class-wp-theme-json-resolver-gutenberg.php
index 93cece68a8d069..ef1b4bcb8481c8 100644
--- a/lib/class-wp-theme-json-resolver-gutenberg.php
+++ b/lib/class-wp-theme-json-resolver-gutenberg.php
@@ -566,7 +566,7 @@ public static function get_merged_data( $origin = 'custom' ) {
 			_deprecated_argument( __FUNCTION__, '5.9.0' );
 		}
 
-		$result = new WP_Theme_JSON();
+		$result = new WP_Theme_JSON_Gutenberg();
 		$result->merge( static::get_core_data() );
 		if ( 'default' === $origin ) {
 			$result->set_spacing_sizes();