diff --git a/composer.json b/composer.json
index fae9e33..0dd4b7f 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
     "require": {
         "php": ">=5.3.2",
         "behat/behat": "~3.0",
-        "atoum/atoum": "~1.0",
+        "atoum/atoum": "~1.0|~2.0",
         "symfony/property-access": "~2.4",
         "justinrainbow/json-schema": "~1.3",
         "egeloen/http-adapter": "^0.8.0"