diff --git a/phpunit b/phpunit
index 74df7131b8..3a39e107db 100755
--- a/phpunit
+++ b/phpunit
@@ -24,15 +24,19 @@ if (!file_exists($COMPOSER = __DIR__.'/composer.phar')) {
 $PHP = ProcessUtils::escapeArgument($PHP);
 $COMPOSER = $PHP.' '.ProcessUtils::escapeArgument($COMPOSER);
 
-if (!file_exists("$PHPUNIT_DIR/phpunit-$PHPUNIT_VERSION/phpunit")) {
+if (!file_exists("$PHPUNIT_DIR/phpunit-$PHPUNIT_VERSION/phpunit") || md5_file(__FILE__) !== @file_get_contents("$PHPUNIT_DIR/.md5") || (isset($argv[1]) && 'install' === $argv[1])) {
     // Build a standalone phpunit without symfony/yaml
 
     $oldPwd = getcwd();
     @mkdir($PHPUNIT_DIR);
     chdir($PHPUNIT_DIR);
+    if (file_exists("phpunit-$PHPUNIT_VERSION")) {
+        passthru(sprintf('\\' === DIRECTORY_SEPARATOR ? 'del /S /F /Q %s & rmdir %1$s >nul 2>&1': 'rm -rf %s', "phpunit-$PHPUNIT_VERSION"));
+    }
     if (extension_loaded('openssl') && ini_get('allow_url_fopen')) {
         stream_copy_to_stream(fopen("https://github.com/sebastianbergmann/phpunit/archive/$PHPUNIT_VERSION.zip", 'rb'), fopen("$PHPUNIT_VERSION.zip", 'wb'));
     } else {
+        @unlink("$PHPUNIT_VERSION.zip");
         passthru("wget https://github.com/sebastianbergmann/phpunit/archive/$PHPUNIT_VERSION.zip");
     }
     $zip = new ZipArchive();
@@ -43,7 +47,14 @@ if (!file_exists("$PHPUNIT_DIR/phpunit-$PHPUNIT_VERSION/phpunit")) {
     passthru("$COMPOSER remove --no-update symfony/yaml");
     passthru("$COMPOSER require --dev --no-update symfony/phpunit-bridge \">=2.8@dev\"");
     passthru("$COMPOSER install --prefer-source --no-progress --ansi");
+    chdir('..');
+    if (file_exists('../src/Symfony/Bridge/PhpUnit') && `git diff --name-only HEAD^ -- ../src/Symfony/Bridge/PhpUnit`) {
+        passthru(sprintf('\\' === DIRECTORY_SEPARATOR ? 'del /S /F /Q %s & rmdir %1$s >nul 2>&1': 'rm -rf %s', str_replace('/', DIRECTORY_SEPARATOR, "phpunit-$PHPUNIT_VERSION/vendor/symfony/phpunit-bridge")));
+        symlink(realpath('../src/Symfony/Bridge/PhpUnit'), "phpunit-$PHPUNIT_VERSION/vendor/symfony/phpunit-bridge");
+    }
+    file_put_contents('.md5', md5_file(__FILE__));
     chdir($oldPwd);
+
 }
 
 $cmd = array_map('Symfony\Component\Process\ProcessUtils::escapeArgument', $argv);