diff --git a/composer.json b/composer.json
index 56372b7..4db5859 100644
--- a/composer.json
+++ b/composer.json
@@ -13,6 +13,7 @@
     }
   ],
   "require": {
+    "php": "^5.6 || ^7.0",
     "phpseclib/phpseclib": "^2.0 !=2.0.8"
   },
   "require-dev": {