diff --git a/composer.json b/composer.json
index 51debc9..1e9414c 100644
--- a/composer.json
+++ b/composer.json
@@ -14,8 +14,8 @@
         "arbiter/arbiter": "~1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7",
-        "zendframework/zend-diactoros": "~1.0"
+        "phpunit/phpunit": "^7.1",
+        "laminas/laminas-diactoros":    "~2.2"
     },
     "autoload": {
         "psr-4": {
diff --git a/tests/Fake/FakeMiddleware.php b/tests/Fake/FakeMiddleware.php
index 8bceaf3..c8a030d 100644
--- a/tests/Fake/FakeMiddleware.php
+++ b/tests/Fake/FakeMiddleware.php
@@ -7,9 +7,9 @@ class FakeMiddleware
 
     public function __invoke($request, $response, $next)
     {
-        $response->getBody()->write(++ static::$count);
+        $response->getBody()->write((string) ++ static::$count);
         $response = $next($request, $response);
-        $response->getBody()->write(++ static::$count);
+        $response->getBody()->write((string) ++ static::$count);
         return $response;
     }
 }