diff --git a/README.md b/README.md
index 75592fb..85071a9 100644
--- a/README.md
+++ b/README.md
@@ -129,9 +129,9 @@ $client->all(array('type' => 'library'));
 $client->all(array('vendor' => 'sylius'));
 ```
 
-#### Custom Packagist Repositories
+#### Custom Packagist repositories
 
-You can also set a custom Packagist Repository URL:
+You can also set a custom Packagist repository URL:
 
 ```php
 <?php
@@ -139,6 +139,11 @@ You can also set a custom Packagist Repository URL:
 $client->setPackagistUrl('https://custom.packagist.site.org');
 ```
 
+## Errors
+
+* A `Packagist\Api\PackageNotFoundException` will be thrown when the Packagist API returns a 404 response.
+* An `\InvalidArgumentException` will be thrown when the respond from Packagist was not able to be parsed.
+
 ## License
 
 `packagist-api` is licensed under the MIT License - see the LICENSE file for details.
diff --git a/spec/Packagist/Api/ClientSpec.php b/spec/Packagist/Api/ClientSpec.php
index 484a3c7..c4b590d 100644
--- a/spec/Packagist/Api/ClientSpec.php
+++ b/spec/Packagist/Api/ClientSpec.php
@@ -5,9 +5,12 @@
 namespace spec\Packagist\Api;
 
 use GuzzleHttp\Client as HttpClient;
+use GuzzleHttp\Exception\ClientException;
+use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\Psr7\Response;
 use GuzzleHttp\Psr7\Stream;
 use Packagist\Api\Client;
+use Packagist\Api\PackageNotFoundException;
 use Packagist\Api\Result\Factory;
 use PhpSpec\ObjectBehavior;
 
@@ -195,4 +198,17 @@ public function it_filters_package_names_by_vendor(HttpClient $client, Factory $
         $this->all(['vendor' => 'sylius']);
     }
 
+    public function it_throws_exception_on_404s(HttpClient $client): void
+    {
+        $request = new Request('GET', 'https://packagist.org/packages/i-do/not-exist.json');
+        $response = new Response(404, [], json_encode(['status' => 'error', 'message' => 'Package not found']));
+        $exception = new ClientException('', $request, $response);
+
+        $client->request('GET', 'https://packagist.org/packages/i-do/not-exist.json')
+            ->shouldBeCalled()
+            ->willThrow($exception);
+
+        $this->shouldThrow(PackageNotFoundException::class)
+            ->during('get', ['i-do/not-exist']);
+    }
 }
diff --git a/src/Packagist/Api/Client.php b/src/Packagist/Api/Client.php
index d5992f0..83e990d 100644
--- a/src/Packagist/Api/Client.php
+++ b/src/Packagist/Api/Client.php
@@ -9,7 +9,6 @@
 use GuzzleHttp\Exception\GuzzleException;
 use Packagist\Api\Result\Factory;
 use Packagist\Api\Result\Package;
-use Psr\Http\Message\StreamInterface;
 
 /**
  * Packagist Api
@@ -247,6 +246,8 @@ protected function multiRespond(string $url1, string $url2)
      *
      * @param string $url
      * @return string
+     * @throws PackageNotFoundException
+     * @throws GuzzleException
      */
     protected function request(string $url): string
     {
@@ -256,7 +257,10 @@ protected function request(string $url): string
                 ->getBody()
                 ->getContents();
         } catch (GuzzleException $e) {
-            return json_encode([]);
+            if ($e->getCode() === 404) {
+                throw new PackageNotFoundException('The requested package was not found.', 404);
+            }
+            throw $e;
         }
     }
 
diff --git a/src/Packagist/Api/PackageNotFoundException.php b/src/Packagist/Api/PackageNotFoundException.php
new file mode 100644
index 0000000..cdb564d
--- /dev/null
+++ b/src/Packagist/Api/PackageNotFoundException.php
@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Packagist\Api;
+
+use InvalidArgumentException;
+
+/**
+ * Thrown when a requested package was not found in the Packagist API.
+ */
+class PackageNotFoundException extends InvalidArgumentException
+{
+}
diff --git a/src/Packagist/Api/Result/Factory.php b/src/Packagist/Api/Result/Factory.php
index 796a8bd..51fabd1 100644
--- a/src/Packagist/Api/Result/Factory.php
+++ b/src/Packagist/Api/Result/Factory.php
@@ -76,15 +76,15 @@ public function createSearchResults(array $results): array
      * @param array $packages
      * @return Package[]
      */
-    public function createComposerPackagesResults(array $packages)
+    public function createComposerPackagesResults(array $packages): array
     {
-        $created = array();
+        $created = [];
 
         foreach ($packages as $name => $package) {
             // Create an empty package, only contains versions
-            $createdPackage = array(
+            $createdPackage = [
                 'versions' => [],
-            );
+            ];
             foreach ($package as $branch => $version) {
                 $createdPackage['versions'][$branch] = $version;
             }