diff --git a/phpunit/class-elements-test.php b/phpunit/class-elements-test.php
index 834512d0625221..349b6328557110 100644
--- a/phpunit/class-elements-test.php
+++ b/phpunit/class-elements-test.php
@@ -13,7 +13,7 @@ class Gutenberg_Elements_Test extends WP_UnitTestCase {
 	 * @return string                String where the unique id classes were replaced with "wp-elements-1".
 	 */
 	private static function make_unique_id_one( $string ) {
-		return preg_replace( '/wp-elements-.{20}/', 'wp-elements-1', $string );
+		return preg_replace( '/wp-elements-.{13}/', 'wp-elements-1', $string );
 	}
 
 	/**