diff --git a/composer.json b/composer.json
index a51df21..dcab3c9 100644
--- a/composer.json
+++ b/composer.json
@@ -13,6 +13,7 @@
     "require": {
         "php": "^7.1",
         "psr/http-message": "^1.0",
+        "php-http/discovery": "^1.4",
         "php-http/message-factory": "^1.0",
         "http-interop/http-factory": "^0.3"
     },