diff --git a/src/Composer/Factory.php b/src/Composer/Factory.php
index 5014b3724..e9b7fbe55 100644
--- a/src/Composer/Factory.php
+++ b/src/Composer/Factory.php
@@ -118,7 +118,7 @@ class Factory
 
     public static function getComposerFile()
     {
-        return getenv('COMPOSER') ?: 'composer.json';
+        return trim(getenv('COMPOSER')) ?: 'composer.json';
     }
 
     public static function createAdditionalStyles()