diff --git a/src/Psy/Command/ComposerCommand.php b/src/Psy/Command/ComposerCommand.php
index 529aef9c2..3deea2909 100644
--- a/src/Psy/Command/ComposerCommand.php
+++ b/src/Psy/Command/ComposerCommand.php
@@ -6,14 +6,22 @@
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\StringInput;
 use Symfony\Component\Console\Output\OutputInterface;
-use Symfony\Component\Process\Process;
 
-/**
- * Class ComposerCommand
- * @package Psy\Command
- */
 class ComposerCommand extends Command
 {
+    const PIPE_WRITE = 0;
+    const PIPE_READ = 1;
+    const PIPE_ERR = 2;
+
+    /**
+     * @var array
+     */
+    protected $specification = array(
+        self::PIPE_WRITE => array("pipe", "r"),
+        self::PIPE_READ => array("pipe", "w"),
+        self::PIPE_ERR => array("pipe", "w"),
+    );
+
     /**
      * @var string
      */
@@ -71,6 +79,9 @@ protected function execute(InputInterface $input, OutputInterface $output)
         return $app->doRun($input, $this->output);
     }
 
+    /**
+     * @param $path
+     */
     public function setComposerPath($path)
     {
         $this->composerPath = $path;
@@ -91,32 +102,65 @@ protected function callComposerBootstrap()
 
     /**
      * @param $command
+     *
      * @return bool|string
      */
     protected function shellCommand($command)
     {
-        /** PHP 5.4 compatibility, closures have no this scope in 5.4 versions */
-        $output = $this->output;
-        $process = new Process($command);
-        $process->run(function ($type, $buffer) use ($output) {
-            if (Process::ERR === $type) {
-                $this->output->writeln("<error>$buffer</error>");
+        $process = proc_open($this->getSystemShell(), $this->specification, $pipes);
+        stream_set_blocking($pipes[self::PIPE_ERR], 0);
+
+        if (is_resource($process)) {
+            fwrite($pipes[self::PIPE_WRITE], $command);
+            fclose($pipes[self::PIPE_WRITE]);
+
+            if ($err = stream_get_contents($pipes[self::PIPE_ERR])) {
+                $err = trim($err);
+                $this->output->writeln("<error>$err</error>");
+
+                return false;
             }
-        });
 
-        return $process->getOutput();
+            $return = stream_get_contents($pipes[self::PIPE_READ]);
+            fclose($pipes[self::PIPE_READ]);
+
+            if (proc_close($process) === 0) {
+                return trim($return);
+            }
+        }
     }
 
+    /**
+     * @return string
+     */
+    protected function getSystemShell()
+    {
+        if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
+            return 'cmd.exe';
+        }
+
+        return 'bash';
+    }
+
+    /**
+     * @return string
+     */
     protected function getLocalComposerFile()
     {
         return getcwd() . DIRECTORY_SEPARATOR . 'composer.phar';
     }
 
+    /**
+     * @return bool
+     */
     protected function checkComposerInstallation()
     {
         return @file_exists($this->getLocalComposerFile()) or !is_null($this->composerPath);
     }
 
+    /**
+     *
+     */
     protected function installComposer()
     {
         $this->output->writeln("<info>Composer not found, downloading.</info>");
diff --git a/src/Psy/Command/SandboxCommand.php b/src/Psy/Command/SandboxCommand.php
index 8d9ff0890..533d644b2 100644
--- a/src/Psy/Command/SandboxCommand.php
+++ b/src/Psy/Command/SandboxCommand.php
@@ -7,10 +7,6 @@
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 
-/**
- * Class SandboxCommand
- * @package Psy\Command
- */
 class SandboxCommand extends Command
 {
     const SANDBOX_FOLDER = 'psysh_sandbox';
@@ -160,6 +156,7 @@ protected function showUsage()
 
     /**
      * @param $name
+     *
      * @return string
      */
     protected function getSandboxPath($name)
@@ -168,7 +165,8 @@ protected function getSandboxPath($name)
     }
 
     /**
-     * @param  null        $name
+     * @param null $name
+     *
      * @return null|string
      */
     protected function createSandbox($name = null)