diff --git a/composer.json b/composer.json
index 7772cc7..8525235 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
     "php": ">=5.4",
     "sabre/xml": "^2.1",
     "symfony/http-foundation": "~2.0|~3.0|~4.0",
-    "nesbot/carbon": "^2.1"
+    "nesbot/carbon": "~1.0"
   },
   "require-dev": {
     "phpspec/phpspec": "~2.1"