diff --git a/tests/docroot/IsUp.php b/tests/docroot/IsUp.php
index e2e69a7..2c1a7d6 100644
--- a/tests/docroot/IsUp.php
+++ b/tests/docroot/IsUp.php
@@ -1,4 +1,4 @@
 <?php return [
     'code'    => 200,
-    'content' => "I'm up!",
+    'content' => getmypid(),
 ];
diff --git a/tests/server.php b/tests/server.php
index 4853613..713e0ee 100644
--- a/tests/server.php
+++ b/tests/server.php
@@ -58,7 +58,7 @@ if (!file_exists($test)) {
 // set the response code
 http_response_code((int) $response['code']);
 // if the response has a body, set the content type and (possibly) the ETag.
-if (strlen($response['content'])) {
+if (strlen((string) $response['content'])) {
     header("Content-Type: ".$response['mime']);
     if ($response['cache']) {
         header('ETag: "'.md5($response['content']).'"');