diff --git a/src/Builder.php b/src/Builder.php
index 4206cd5..35fb1bb 100644
--- a/src/Builder.php
+++ b/src/Builder.php
@@ -81,7 +81,7 @@ public function saveFiles()
         $this->writeConfig('__addition', $this->addition);
     }
 
-    public static function rebuild($outputDir)
+    public static function rebuild($outputDir = null)
     {
         $builder = new self([], $outputDir);
         $builder->loadFiles();
@@ -123,7 +123,7 @@ public function buildConfigs($files = null)
             }
             $this->buildConfig($name, $configs);
         }
-        file_put_contents($this->getOutputPath('__rebuild'), file_get_contents(__DIR__ . DIRECTORY_SEPARATOR . '__rebuild.php'));
+        static::putFile($this->getOutputPath('__rebuild'), file_get_contents(__DIR__ . DIRECTORY_SEPARATOR . '__rebuild.php'));
     }
 
     /**
@@ -186,10 +186,12 @@ public static function writeFile($path, array $data)
      */
     protected static function putFile($path, $content)
     {
-        if (file_exists($path) && $content = file_get_contents($path)) {
+        if (file_exists($path) && $content === file_get_contents($path)) {
             return;
         }
-        file_put_contents($path, $content);
+        if (file_put_contents($path, $content) === FALSE) {
+            throw new FailedWriteException("Failed write file $path");
+        }
     }
 
     /**
diff --git a/src/FailedWriteException.php b/src/FailedWriteException.php
new file mode 100644
index 0000000..e0738bd
--- /dev/null
+++ b/src/FailedWriteException.php
@@ -0,0 +1,20 @@
+<?php
+/**
+ * Composer plugin for config assembling
+ *
+ * @link      https://github.com/hiqdev/composer-config-plugin
+ * @package   composer-config-plugin
+ * @license   BSD-3-Clause
+ * @copyright Copyright (c) 2016, HiQDev (http://hiqdev.com/)
+ */
+
+namespace hiqdev\composer\config;
+
+/**
+ * Failed write file exception.
+ *
+ * @author Andrii Vasyliev <sol@hiqdev.com>
+ */
+class FailedWriteException extends \Exception
+{
+}