diff --git a/composer.json b/composer.json
index f700cb9..5789e1d 100644
--- a/composer.json
+++ b/composer.json
@@ -8,7 +8,8 @@
     "require": {
         "php": ">=5.5.9",
         "guzzlehttp/guzzle": "~6.0",
-        "fzaninotto/faker": "^1.6"
+        "fzaninotto/faker": "^1.6",
+        "ext-json": "*"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.7",