diff --git a/Slim/Middleware/OutputBufferingMiddleware.php b/Slim/Middleware/OutputBufferingMiddleware.php
index b93374085..71dfd057a 100644
--- a/Slim/Middleware/OutputBufferingMiddleware.php
+++ b/Slim/Middleware/OutputBufferingMiddleware.php
@@ -63,12 +63,12 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
             throw $e;
         }
 
-        if (!empty($output) && $response->getBody()->isWritable()) {
+        if (!empty($output)) {
             if ($this->style === static::PREPEND) {
                 $body = $this->streamFactory->createStream();
                 $body->write($output . $response->getBody());
                 $response = $response->withBody($body);
-            } elseif ($this->style === static::APPEND) {
+            } elseif ($this->style === static::APPEND && $response->getBody()->isWritable()) {
                 $response->getBody()->write($output);
             }
         }