diff --git a/composer.json b/composer.json
index 504a2db..bc541bc 100644
--- a/composer.json
+++ b/composer.json
@@ -5,6 +5,7 @@
         "php": "^5.5|^7.0",
         "php-http/httplug": "^1.0",
         "php-http/multipart-stream-builder": "^0.1",
+        "php-http/message": "^1.0",
         "php-http/discovery": "^1.0"
     },
     "require-dev": {