diff --git a/composer.json b/composer.json
index fd4f366..0c0513d 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
     "type": "library",
     "require": {
 	    "php": ">=5.5.9",
-        "greenter/core": "^1.2"
+        "greenter/core": "^2.1"
     },
 	"require-dev": {
         "phpunit/phpunit": ">=4.8 < 6.0"