diff --git a/composer.json b/composer.json
index 3f6a3984e7a42a1102cbe242108735089356da8f..12afeb19c697a894c77ff7d81efbf6267acaa1a3 100644
--- a/composer.json
+++ b/composer.json
@@ -7,7 +7,8 @@
         "code-style": "phpcs --standard=PSR2 src && phpcs --standard=PSR2 --ignore=example tests"
     },
     "require": {
-        "guzzlehttp/psr7": "^1.4.2"
+        "guzzlehttp/psr7": "^1.4.2",
+        "ralouphie/getallheaders": "^2.0.5"
     },
     "require-dev": {
         "phpunit/phpunit": "^7.2.7",