diff --git a/src/ChronosInterface.php b/src/ChronosInterface.php
index 8e8b5d13..fa7a4738 100644
--- a/src/ChronosInterface.php
+++ b/src/ChronosInterface.php
@@ -102,7 +102,7 @@ interface ChronosInterface extends DateTimeInterface
      * @param \DateTimeZone|string|null $tz The DateTimeZone object or timezone name.
      * @return static
      */
-    public static function now($tz): self;
+    public static function now($tz = null): self;
 
     /**
      * Get a copy of the instance
diff --git a/tests/TestCase/Date/StringsTest.php b/tests/TestCase/Date/StringsTest.php
index edeb338d..abc8f4c0 100644
--- a/tests/TestCase/Date/StringsTest.php
+++ b/tests/TestCase/Date/StringsTest.php
@@ -18,6 +18,11 @@
 
 class StringsTest extends TestCase
 {
+    /**
+     * @var string
+     */
+    protected $tz;
+
     /**
      * Setup
      *