diff --git a/system/defines.php b/system/defines.php
index 9f2975723..14993a8ae 100644
--- a/system/defines.php
+++ b/system/defines.php
@@ -12,6 +12,10 @@ define('GRAV_VERSION', '1.1.16');
 define('GRAV_TESTING', false);
 define('DS', '/');
 
+if (!defined('GRAV_PHP_MIN')) {
+    define('GRAV_PHP_MIN', '5.5.9');
+}
+
 // Directories and Paths
 if (!defined('GRAV_ROOT')) {
     define('GRAV_ROOT', str_replace(DIRECTORY_SEPARATOR, DS, getcwd()));