diff --git a/module/Core/src/Middleware/QrCodeCacheMiddleware.php b/module/Core/src/Middleware/QrCodeCacheMiddleware.php
index d0f132bb..67e9bdab 100644
--- a/module/Core/src/Middleware/QrCodeCacheMiddleware.php
+++ b/module/Core/src/Middleware/QrCodeCacheMiddleware.php
@@ -3,9 +3,11 @@ namespace Shlinkio\Shlink\Core\Middleware;
 
 use Acelaya\ZsmAnnotatedServices\Annotation\Inject;
 use Doctrine\Common\Cache\Cache;
+use Interop\Http\ServerMiddleware\DelegateInterface;
+use Interop\Http\ServerMiddleware\MiddlewareInterface;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
-use Zend\Stratigility\MiddlewareInterface;
+use Zend\Diactoros\Response as DiactResp;
 
 class QrCodeCacheMiddleware implements MiddlewareInterface
 {
@@ -26,44 +28,29 @@ class QrCodeCacheMiddleware implements MiddlewareInterface
     }
 
     /**
-     * Process an incoming request and/or response.
-     *
-     * Accepts a server-side request and a response instance, and does
-     * something with them.
-     *
-     * If the response is not complete and/or further processing would not
-     * interfere with the work done in the middleware, or if the middleware
-     * wants to delegate to another process, it can use the `$out` callable
-     * if present.
-     *
-     * If the middleware does not return a value, execution of the current
-     * request is considered complete, and the response instance provided will
-     * be considered the response to return.
-     *
-     * Alternately, the middleware may return a response instance.
-     *
-     * Often, middleware will `return $out();`, with the assumption that a
-     * later middleware will return a response.
+     * Process an incoming server request and return a response, optionally delegating
+     * to the next middleware component to create the response.
      *
      * @param Request $request
-     * @param Response $response
-     * @param null|callable $out
-     * @return null|Response
+     * @param DelegateInterface $delegate
+     *
+     * @return Response
      */
-    public function __invoke(Request $request, Response $response, callable $out = null)
+    public function process(Request $request, DelegateInterface $delegate)
     {
         $cacheKey = $request->getUri()->getPath();
 
         // If this QR code is already cached, just return it
         if ($this->cache->contains($cacheKey)) {
             $qrData = $this->cache->fetch($cacheKey);
+            $response = new DiactResp();
             $response->getBody()->write($qrData['body']);
             return $response->withHeader('Content-Type', $qrData['content-type']);
         }
 
         // If not, call the next middleware and cache it
         /** @var Response $resp */
-        $resp = $out($request, $response);
+        $resp = $delegate->process($request);
         $this->cache->save($cacheKey, [
             'body' => $resp->getBody()->__toString(),
             'content-type' => $resp->getHeaderLine('Content-Type'),
diff --git a/module/Core/test/Middleware/QrCodeCacheMiddlewareTest.php b/module/Core/test/Middleware/QrCodeCacheMiddlewareTest.php
index 50c2e736..abc1801d 100644
--- a/module/Core/test/Middleware/QrCodeCacheMiddlewareTest.php
+++ b/module/Core/test/Middleware/QrCodeCacheMiddlewareTest.php
@@ -4,7 +4,9 @@ namespace ShlinkioTest\Shlink\Core\Middleware;
 use Doctrine\Common\Cache\ArrayCache;
 use Doctrine\Common\Cache\Cache;
 use PHPUnit\Framework\TestCase;
+use Prophecy\Argument;
 use Shlinkio\Shlink\Core\Middleware\QrCodeCacheMiddleware;
+use ShlinkioTest\Shlink\Common\Util\TestUtils;
 use Zend\Diactoros\Response;
 use Zend\Diactoros\ServerRequestFactory;
 use Zend\Diactoros\Uri;
@@ -29,18 +31,15 @@ class QrCodeCacheMiddlewareTest extends TestCase
     /**
      * @test
      */
-    public function noCachedPathFallbacksToNextMiddleware()
+    public function noCachedPathFallsBackToNextMiddleware()
     {
-        $isCalled = false;
-        $this->middleware->__invoke(
-            ServerRequestFactory::fromGlobals(),
-            new Response(),
-            function ($req, $resp) use (&$isCalled) {
-                $isCalled = true;
-                return $resp;
-            }
-        );
-        $this->assertTrue($isCalled);
+        $delegate = TestUtils::createDelegateMock();
+        $this->middleware->process(ServerRequestFactory::fromGlobals()->withUri(
+            new Uri('/foo/bar')
+        ), $delegate->reveal());
+
+        $this->assertTrue($this->cache->contains('/foo/bar'));
+        $delegate->process(Argument::any())->shouldHaveBeenCalledTimes(1);
     }
 
     /**
@@ -51,19 +50,17 @@ class QrCodeCacheMiddlewareTest extends TestCase
         $isCalled = false;
         $uri = (new Uri())->withPath('/foo');
         $this->cache->save('/foo', ['body' => 'the body', 'content-type' => 'image/png']);
+        $delegate = TestUtils::createDelegateMock();
 
-        $resp = $this->middleware->__invoke(
+        $resp = $this->middleware->process(
             ServerRequestFactory::fromGlobals()->withUri($uri),
-            new Response(),
-            function ($req, $resp) use (&$isCalled) {
-                $isCalled = true;
-                return $resp;
-            }
+            $delegate->reveal()
         );
 
         $this->assertFalse($isCalled);
         $resp->getBody()->rewind();
         $this->assertEquals('the body', $resp->getBody()->getContents());
         $this->assertEquals('image/png', $resp->getHeaderLine('Content-Type'));
+        $delegate->process(Argument::any())->shouldHaveBeenCalledTimes(0);
     }
 }