diff --git a/lib/composer/composer/ClassLoader.php b/lib/composer/composer/ClassLoader.php
index ff6ecfb822f89ab498410e4d8dd1e6204f15dd8d..ac67d302a1866f83aab0c3bff265cfbfe9318f51 100644
--- a/lib/composer/composer/ClassLoader.php
+++ b/lib/composer/composer/ClassLoader.php
@@ -53,8 +53,8 @@ class ClassLoader
 
     private $useIncludePath = false;
     private $classMap = array();
-
     private $classMapAuthoritative = false;
+    private $missingClasses = array();
 
     public function getPrefixes()
     {
@@ -322,20 +322,20 @@ class ClassLoader
         if (isset($this->classMap[$class])) {
             return $this->classMap[$class];
         }
-        if ($this->classMapAuthoritative) {
+        if ($this->classMapAuthoritative || isset($this->missingClasses[$class])) {
             return false;
         }
 
         $file = $this->findFileWithExtension($class, '.php');
 
         // Search for Hack files if we are running on HHVM
-        if ($file === null && defined('HHVM_VERSION')) {
+        if (false === $file && defined('HHVM_VERSION')) {
             $file = $this->findFileWithExtension($class, '.hh');
         }
 
-        if ($file === null) {
+        if (false === $file) {
             // Remember that this class does not exist.
-            return $this->classMap[$class] = false;
+            $this->missingClasses[$class] = true;
         }
 
         return $file;
@@ -399,6 +399,8 @@ class ClassLoader
         if ($this->useIncludePath && $file = stream_resolve_include_path($logicalPathPsr0)) {
             return $file;
         }
+
+        return false;
     }
 }
 
diff --git a/tests/phpunit.xml.dist b/tests/phpunit.xml.dist
deleted file mode 100644
index d3a5897dfaf446e576ed7f30c8b52ed3e433da10..0000000000000000000000000000000000000000
--- a/tests/phpunit.xml.dist
+++ /dev/null
@@ -1,36 +0,0 @@
-<?xml version="1.0" encoding="utf-8" ?>
-<phpunit bootstrap="bootstrap.php">
-	<testsuite name='ownCloud'>
-		<directory suffix='.php'>lib/</directory>
-		<directory suffix='.php'>Settings/</directory>
-		<directory suffix='.php'>Core/</directory>
-		<file>apps.php</file>
-	</testsuite>
-	<!-- filters for code coverage -->
-	<filter>
-		<!-- whitelist processUncoveredFilesFromWhitelist="true" -->
-		<whitelist>
-			<directory suffix=".php">..</directory>
-			<exclude>
-				<directory suffix=".php">../3rdparty</directory>
-				<directory suffix=".php">../apps/files/l10n</directory>
-				<directory suffix=".php">../apps/files_external/l10n</directory>
-				<directory suffix=".php">../apps/files_external/3rdparty</directory>
-				<directory suffix=".php">../apps/files_versions/l10n</directory>
-				<directory suffix=".php">../apps/encryption/l10n</directory>
-				<directory suffix=".php">../apps/files_sharing/l10n</directory>
-				<directory suffix=".php">../apps/files_trashbin/l10n</directory>
-				<directory suffix=".php">../apps/user_ldap/l10n</directory>
-				<directory suffix=".php">../apps/user_webdavauth/l10n</directory>
-				<directory suffix=".php">../apps/provisioning_api/tests</directory>
-				<directory suffix=".php">../lib/l10n</directory>
-				<directory suffix=".php">../core/l10n</directory>
-				<directory suffix=".php">../settings/l10n</directory>
-				<directory suffix=".php">../tests</directory>
-			</exclude>
-		</whitelist>
-	</filter>
-	<listeners>
-		<listener class="StartSessionListener" file="startsessionlistener.php" />
-	</listeners>
-</phpunit>