diff --git a/composer.json b/composer.json
index ddd0b17..df582c0 100644
--- a/composer.json
+++ b/composer.json
@@ -23,6 +23,9 @@
         "friendsofphp/php-cs-fixer": "^1.13|^2.16",
         "phpunit/phpunit": "<4.8.35|<5.4.3,>=5.0"
     },
+    "suggest": {
+        "ext-posix": "In order to get the real user ID of the current process."
+    },
     "autoload": {
         "psr-4": { "ZabbixApi\\": ["src/"] }
     },