diff --git a/composer.json b/composer.json
index 0af63c7..88abc0b 100644
--- a/composer.json
+++ b/composer.json
@@ -10,6 +10,9 @@
         }
     ],
     "minimum-stability": "dev",
+    "require": {
+        "php": ">=5.6.4"
+    },
     "autoload": {
         "psr-4": {
             "Salman\\Mqtt\\": "src/"