diff --git a/src/Middleware/AddHttp2ServerPush.php b/src/Middleware/AddHttp2ServerPush.php
index 167d1c6..ac3fd26 100644
--- a/src/Middleware/AddHttp2ServerPush.php
+++ b/src/Middleware/AddHttp2ServerPush.php
@@ -109,7 +109,7 @@ private function buildLinkHeaderString($url)
             '.TIFF' => 'image',
         ];
 
-        $type = collect($linkTypeMap)->first(function ($extension) use ($url) {
+        $type = collect($linkTypeMap)->first(function ($type, $extension) use ($url) {
             return str_contains(strtoupper($url), $extension);
         });
 
diff --git a/tests/AddHttp2ServerPushTest.php b/tests/AddHttp2ServerPushTest.php
index 99502c8..c15eed1 100644
--- a/tests/AddHttp2ServerPushTest.php
+++ b/tests/AddHttp2ServerPushTest.php
@@ -49,7 +49,7 @@ public function it_will_return_a_js_link_header_for_js()
     }
 
     /** @test */
-    public function it_will_return_a_image_link_header_for_images()
+    public function it_will_return_an_image_link_header_for_images()
     {
         $request = new Request();
 
@@ -57,7 +57,7 @@ public function it_will_return_a_image_link_header_for_images()
 
         $this->assertTrue($this->isServerPushResponse($response));
         $this->assertStringEndsWith("as=image", $response->headers->get('link'));
-        $this->assertCount(6, explode(",", $response->headers));
+        $this->assertCount(6, explode(",", $response->headers->get('link')));
     }
 
     /** @test */
@@ -80,7 +80,7 @@ public function it_will_return_correct_push_headers_for_multiple_assets()
         $this->assertTrue($this->isServerPushResponse($response));
         $this->assertTrue(str_contains($response->headers, 'style'));
         $this->assertTrue(str_contains($response->headers, 'script'));
-        $this->assertCount(2, explode(",", $response->headers));
+        $this->assertCount(2, explode(",", $response->headers->get('link')));
     }
 
     /** @test */