diff --git a/composer_manager.drush.inc b/composer_manager.drush.inc
index 66dc5ee..f7f9b5f 100644
--- a/composer_manager.drush.inc
+++ b/composer_manager.drush.inc
@@ -76,10 +76,15 @@ function drush_composer_manager($command = 'install') {
 
   // Generate the command arguments to pass to Drush Composer.
   $drush_arguments = drush_get_arguments();
+
+  if (strtoupper(substr(PHP_OS, 0, 3)) !== 'WIN') {
+    $dir = escapeshellcmd($dir);
+  }
+
   if ($drush_arguments && $drush_arguments[0] === 'composer-manager') {
     $arguments = $drush_arguments;
-    array_shift($arguments); // exclude drush main command, composer-manager 
-    $arguments[] = '--working-dir=' . escapeshellcmd($dir);
+    array_shift($arguments); // exclude drush main command, composer-manager
+    $arguments[] = '--working-dir=' . $dir;
   }
   else {
     $arguments = array(
@@ -87,7 +92,7 @@ function drush_composer_manager($command = 'install') {
       // The use of escapeshellcmd rather than escapeshellarg is necessary to
       // avoid enclosing the value in quotes, which is incompatible with the way
       // Composer validates that the working directory exists.
-      '--working-dir=' . escapeshellcmd($dir),
+      '--working-dir=' . $dir,
     );
   }