diff --git a/module/Rest/src/Middleware/BackwardsCompatibleProblemDetailsMiddleware.php b/module/Rest/src/Middleware/BackwardsCompatibleProblemDetailsMiddleware.php
index 9857465b..0812c7e0 100644
--- a/module/Rest/src/Middleware/BackwardsCompatibleProblemDetailsMiddleware.php
+++ b/module/Rest/src/Middleware/BackwardsCompatibleProblemDetailsMiddleware.php
@@ -36,7 +36,6 @@ class BackwardsCompatibleProblemDetailsMiddleware implements MiddlewareInterface
     public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
     {
         $resp = $handler->handle($request);
-
         if ($resp->getHeaderLine('Content-type') !== 'application/problem+json') {
             return $resp;
         }
@@ -70,9 +69,7 @@ class BackwardsCompatibleProblemDetailsMiddleware implements MiddlewareInterface
     /** @deprecated When Shlink 2 is released, do not chekc the version */
     private function isVersionOne(ServerRequestInterface $request): bool
     {
-        $uri = $request->getUri();
-        $path = $uri->getPath();
-
+        $path = $request->getUri()->getPath();
         return strpos($path, '/v') === false || strpos($path, '/v1') === 0;
     }
 
diff --git a/module/Rest/test/Middleware/BackwardsCompatibleProblemDetailsMiddlewareTest.php b/module/Rest/test/Middleware/BackwardsCompatibleProblemDetailsMiddlewareTest.php
new file mode 100644
index 00000000..4d47c4cb
--- /dev/null
+++ b/module/Rest/test/Middleware/BackwardsCompatibleProblemDetailsMiddlewareTest.php
@@ -0,0 +1,122 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ShlinkioTest\Shlink\Rest\Middleware;
+
+use PHPUnit\Framework\TestCase;
+use Prophecy\Prophecy\ObjectProphecy;
+use Psr\Http\Server\RequestHandlerInterface;
+use Shlinkio\Shlink\Rest\Middleware\BackwardsCompatibleProblemDetailsMiddleware;
+use Zend\Diactoros\Response;
+use Zend\Diactoros\ServerRequestFactory;
+use Zend\Diactoros\Uri;
+
+class BackwardsCompatibleProblemDetailsMiddlewareTest extends TestCase
+{
+    /** @var BackwardsCompatibleProblemDetailsMiddleware */
+    private $middleware;
+    /** @var ObjectProphecy */
+    private $handler;
+
+    public function setUp(): void
+    {
+        $this->handler = $this->prophesize(RequestHandlerInterface::class);
+        $this->middleware = new BackwardsCompatibleProblemDetailsMiddleware([
+            404 => 'NOT_FOUND',
+            500 => 'INTERNAL_SERVER_ERROR',
+        ], 0);
+    }
+
+    /**
+     * @test
+     * @dataProvider provideNonProcessableResponses
+     */
+    public function nonProblemDetailsOrInvalidResponsesAreReturnedAsTheyAre(Response $response): void
+    {
+        $request = ServerRequestFactory::fromGlobals();
+        $response = new Response();
+        $handle = $this->handler->handle($request)->willReturn($response);
+
+        $result = $this->middleware->process($request, $this->handler->reveal());
+
+        $this->assertSame($response, $result);
+        $handle->shouldHaveBeenCalledOnce();
+    }
+
+    public function provideNonProcessableResponses(): iterable
+    {
+        yield 'no problem details' => [new Response()];
+        yield 'invalid JSON' => [(new Response('data://text/plain,{invalid-json'))->withHeader(
+            'Content-Type',
+            'application/problem+json'
+        )];
+    }
+
+    /**
+     * @test
+     * @dataProvider provideStatusAndTypes
+     */
+    public function properlyMapsTypesBasedOnResponseStatus(Response\JsonResponse $response, string $expectedType): void
+    {
+        $request = ServerRequestFactory::fromGlobals()->withUri(new Uri('/v2/something'));
+        $handle = $this->handler->handle($request)->willReturn($response);
+
+        /** @var Response\JsonResponse $result */
+        $result = $this->middleware->process($request, $this->handler->reveal());
+        $payload = $result->getPayload();
+
+        $this->assertEquals($expectedType, $payload['type']);
+        $this->assertArrayNotHasKey('error', $payload);
+        $this->assertArrayNotHasKey('message', $payload);
+        $handle->shouldHaveBeenCalledOnce();
+    }
+
+    public function provideStatusAndTypes(): iterable
+    {
+        yield [$this->jsonResponse(['type' => 'https://httpstatus.es/404'], 404), 'NOT_FOUND'];
+        yield [$this->jsonResponse(['type' => 'https://httpstatus.es/500'], 500), 'INTERNAL_SERVER_ERROR'];
+        yield [$this->jsonResponse(['type' => 'https://httpstatus.es/504'], 504), 'https://httpstatus.es/504'];
+        yield [$this->jsonResponse(['type' => 'something_else'], 404), 'something_else'];
+        yield [$this->jsonResponse(['type' => 'something_else'], 500), 'something_else'];
+        yield [$this->jsonResponse(['type' => 'something_else'], 504), 'something_else'];
+    }
+
+    /**
+     * @test
+     * @dataProvider provideRequestPath
+     */
+    public function mapsDeprecatedPropertiesWhenRequestIsPerformedToVersionOne(string $requestPath): void
+    {
+        $request = ServerRequestFactory::fromGlobals()->withUri(new Uri($requestPath));
+        $response = $this->jsonResponse([
+            'type' => 'the_type',
+            'detail' => 'the_detail',
+        ]);
+        $handle = $this->handler->handle($request)->willReturn($response);
+
+        /** @var Response\JsonResponse $result */
+        $result = $this->middleware->process($request, $this->handler->reveal());
+        $payload = $result->getPayload();
+
+        $this->assertEquals([
+            'type' => 'the_type',
+            'detail' => 'the_detail',
+            'error' => 'the_type',
+            'message' => 'the_detail',
+        ], $payload);
+        $handle->shouldHaveBeenCalledOnce();
+    }
+
+    public function provideRequestPath(): iterable
+    {
+        yield 'no version' => ['/foo'];
+        yield 'version one' => ['/v1/foo'];
+    }
+
+    private function jsonResponse(array $payload, int $status = 200): Response\JsonResponse
+    {
+        $headers = ['Content-Type' => 'application/problem+json'];
+        return new Response\JsonResponse($payload, $status, $headers);
+    }
+}