diff --git a/src/Printer8.php b/src/Printer8.php
index ed51138..cf88392 100644
--- a/src/Printer8.php
+++ b/src/Printer8.php
@@ -17,7 +17,7 @@ class Printer8 extends ResultPrinter
      */
     private $currentType;
 
-    protected function printHeader(TestResult $result): void
+    protected function printHeader(TestResult $result = null): void
     {
     }