diff --git a/apps/accessibility/composer/composer/ClassLoader.php b/apps/accessibility/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/accessibility/composer/composer/ClassLoader.php
+++ b/apps/accessibility/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/admin_audit/composer/composer/ClassLoader.php b/apps/admin_audit/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/admin_audit/composer/composer/ClassLoader.php
+++ b/apps/admin_audit/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/cloud_federation_api/composer/composer/ClassLoader.php b/apps/cloud_federation_api/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/cloud_federation_api/composer/composer/ClassLoader.php
+++ b/apps/cloud_federation_api/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/comments/composer/composer/ClassLoader.php b/apps/comments/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/comments/composer/composer/ClassLoader.php
+++ b/apps/comments/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/contactsinteraction/composer/composer/ClassLoader.php b/apps/contactsinteraction/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/contactsinteraction/composer/composer/ClassLoader.php
+++ b/apps/contactsinteraction/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/dav/composer/composer/ClassLoader.php b/apps/dav/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/dav/composer/composer/ClassLoader.php
+++ b/apps/dav/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/encryption/composer/composer/ClassLoader.php b/apps/encryption/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/encryption/composer/composer/ClassLoader.php
+++ b/apps/encryption/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/federatedfilesharing/composer/composer/ClassLoader.php b/apps/federatedfilesharing/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/federatedfilesharing/composer/composer/ClassLoader.php
+++ b/apps/federatedfilesharing/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/federation/composer/composer/ClassLoader.php b/apps/federation/composer/composer/ClassLoader.php
index 247294d66e..03b9bb9c40 100644
--- a/apps/federation/composer/composer/ClassLoader.php
+++ b/apps/federation/composer/composer/ClassLoader.php
@@ -37,13 +37,11 @@ namespace Composer\Autoload;
  *
  * @author Fabien Potencier <fabien@symfony.com>
  * @author Jordi Boggiano <j.boggiano@seld.be>
- * @see    https://www.php-fig.org/psr/psr-0/
- * @see    https://www.php-fig.org/psr/psr-4/
+ * @see    http://www.php-fig.org/psr/psr-0/
+ * @see    http://www.php-fig.org/psr/psr-4/
  */
 class ClassLoader
 {
-    private $vendorDir;
-
     // PSR-4
     private $prefixLengthsPsr4 = array();
     private $prefixDirsPsr4 = array();
@@ -59,13 +57,6 @@ class ClassLoader
     private $missingClasses = array();
     private $apcuPrefix;
 
-    private static $registeredLoaders = array();
-
-    public function __construct($vendorDir = null)
-    {
-        $this->vendorDir = $vendorDir;
-    }
-
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
@@ -309,17 +300,6 @@ class ClassLoader
     public function register($prepend = false)
     {
         spl_autoload_register(array($this, 'loadClass'), true, $prepend);
-
-        if (null === $this->vendorDir) {
-            return;
-        }
-
-        if ($prepend) {
-            self::$registeredLoaders = array($this->vendorDir => $this) + self::$registeredLoaders;
-        } else {
-            unset(self::$registeredLoaders[$this->vendorDir]);
-            self::$registeredLoaders[$this->vendorDir] = $this;
-        }
     }
 
     /**
@@ -328,10 +308,6 @@ class ClassLoader
     public function unregister()
     {
         spl_autoload_unregister(array($this, 'loadClass'));
-
-        if (null !== $this->vendorDir) {
-            unset(self::$registeredLoaders[$this->vendorDir]);
-        }
     }
 
     /**
@@ -391,16 +367,6 @@ class ClassLoader
         return $file;
     }
 
-    /**
-     * Returns the currently registered loaders indexed by their corresponding vendor directories.
-     *
-     * @return self[]
-     */
-    public static function getRegisteredLoaders()
-    {
-        return self::$registeredLoaders;
-    }
-
     private function findFileWithExtension($class, $ext)
     {
         // PSR-4 lookup
diff --git a/apps/federation/composer/composer/autoload_classmap.php b/apps/federation/composer/composer/autoload_classmap.php
index 18cc80e31a..3a634db22d 100644
--- a/apps/federation/composer/composer/autoload_classmap.php
+++ b/apps/federation/composer/composer/autoload_classmap.php
@@ -6,7 +6,6 @@ $vendorDir = dirname(dirname(__FILE__));
 $baseDir = $vendorDir;
 
 return array(
-    'Composer\\InstalledVersions' => $vendorDir . '/composer/InstalledVersions.php',
     'OCA\\Federation\\AppInfo\\Application' => $baseDir . '/../lib/AppInfo/Application.php',
     'OCA\\Federation\\BackgroundJob\\GetSharedSecret' => $baseDir . '/../lib/BackgroundJob/GetSharedSecret.php',
     'OCA\\Federation\\BackgroundJob\\RequestSharedSecret' => $baseDir . '/../lib/BackgroundJob/RequestSharedSecret.php',
diff --git a/apps/federation/composer/composer/autoload_real.php b/apps/federation/composer/composer/autoload_real.php
index fed3f44342..75b98c785d 100644
--- a/apps/federation/composer/composer/autoload_real.php
+++ b/apps/federation/composer/composer/autoload_real.php
@@ -23,12 +23,12 @@ class ComposerAutoloaderInitFederation
         }
 
         spl_autoload_register(array('ComposerAutoloaderInitFederation', 'loadClassLoader'), true, true);
-        self::$loader = $loader = new \Composer\Autoload\ClassLoader(\dirname(\dirname(__FILE__)));
+        self::$loader = $loader = new \Composer\Autoload\ClassLoader();
         spl_autoload_unregister(array('ComposerAutoloaderInitFederation', 'loadClassLoader'));
 
         $useStaticLoader = PHP_VERSION_ID >= 50600 && !defined('HHVM_VERSION') && (!function_exists('zend_loader_file_encoded') || !zend_loader_file_encoded());
         if ($useStaticLoader) {
-            require __DIR__ . '/autoload_static.php';
+            require_once __DIR__ . '/autoload_static.php';
 
             call_user_func(\Composer\Autoload\ComposerStaticInitFederation::getInitializer($loader));
         } else {
diff --git a/apps/federation/composer/composer/autoload_static.php b/apps/federation/composer/composer/autoload_static.php
index 80fc75771b..8eab580a8d 100644
--- a/apps/federation/composer/composer/autoload_static.php
+++ b/apps/federation/composer/composer/autoload_static.php
@@ -21,7 +21,6 @@ class ComposerStaticInitFederation
     );
 
     public static $classMap = array (
-        'Composer\\InstalledVersions' => __DIR__ . '/..' . '/composer/InstalledVersions.php',
         'OCA\\Federation\\AppInfo\\Application' => __DIR__ . '/..' . '/../lib/AppInfo/Application.php',
         'OCA\\Federation\\BackgroundJob\\GetSharedSecret' => __DIR__ . '/..' . '/../lib/BackgroundJob/GetSharedSecret.php',
         'OCA\\Federation\\BackgroundJob\\RequestSharedSecret' => __DIR__ . '/..' . '/../lib/BackgroundJob/RequestSharedSecret.php',
diff --git a/apps/files/composer/composer/ClassLoader.php b/apps/files/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/files/composer/composer/ClassLoader.php
+++ b/apps/files/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/files_sharing/composer/composer/ClassLoader.php b/apps/files_sharing/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/files_sharing/composer/composer/ClassLoader.php
+++ b/apps/files_sharing/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/files_trashbin/composer/composer/ClassLoader.php b/apps/files_trashbin/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/files_trashbin/composer/composer/ClassLoader.php
+++ b/apps/files_trashbin/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/files_versions/composer/composer/ClassLoader.php b/apps/files_versions/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/files_versions/composer/composer/ClassLoader.php
+++ b/apps/files_versions/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/lookup_server_connector/composer/composer/ClassLoader.php b/apps/lookup_server_connector/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/lookup_server_connector/composer/composer/ClassLoader.php
+++ b/apps/lookup_server_connector/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/oauth2/composer/composer/ClassLoader.php b/apps/oauth2/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/oauth2/composer/composer/ClassLoader.php
+++ b/apps/oauth2/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/provisioning_api/composer/composer/ClassLoader.php b/apps/provisioning_api/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/provisioning_api/composer/composer/ClassLoader.php
+++ b/apps/provisioning_api/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/settings/composer/composer/ClassLoader.php b/apps/settings/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/settings/composer/composer/ClassLoader.php
+++ b/apps/settings/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/sharebymail/composer/composer/ClassLoader.php b/apps/sharebymail/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/sharebymail/composer/composer/ClassLoader.php
+++ b/apps/sharebymail/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/systemtags/composer/composer/ClassLoader.php b/apps/systemtags/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/systemtags/composer/composer/ClassLoader.php
+++ b/apps/systemtags/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/testing/composer/composer/ClassLoader.php b/apps/testing/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/testing/composer/composer/ClassLoader.php
+++ b/apps/testing/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/twofactor_backupcodes/composer/composer/ClassLoader.php b/apps/twofactor_backupcodes/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/twofactor_backupcodes/composer/composer/ClassLoader.php
+++ b/apps/twofactor_backupcodes/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/updatenotification/composer/composer/ClassLoader.php b/apps/updatenotification/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/updatenotification/composer/composer/ClassLoader.php
+++ b/apps/updatenotification/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/user_ldap/composer/composer/ClassLoader.php b/apps/user_ldap/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/user_ldap/composer/composer/ClassLoader.php
+++ b/apps/user_ldap/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/apps/workflowengine/composer/composer/ClassLoader.php b/apps/workflowengine/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/apps/workflowengine/composer/composer/ClassLoader.php
+++ b/apps/workflowengine/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();
diff --git a/lib/composer/composer/ClassLoader.php b/lib/composer/composer/ClassLoader.php
index fce8549f07..03b9bb9c40 100644
--- a/lib/composer/composer/ClassLoader.php
+++ b/lib/composer/composer/ClassLoader.php
@@ -60,7 +60,7 @@ class ClassLoader
     public function getPrefixes()
     {
         if (!empty($this->prefixesPsr0)) {
-            return call_user_func_array('array_merge', $this->prefixesPsr0);
+            return call_user_func_array('array_merge', array_values($this->prefixesPsr0));
         }
 
         return array();