diff --git a/composer.json b/composer.json
index 01e52df..9950539 100644
--- a/composer.json
+++ b/composer.json
@@ -16,6 +16,7 @@
     }
   ],
   "require": {
+    "php": ">=7.1",
     "mikehaertl/php-shellcommand": "1.*",
     "yiisoft/yii2": "2.*",
     "schmunk42/retry" : "*"
diff --git a/db/helper/CliHelper.php b/db/helper/CliHelper.php
index e324b0a..6d95b50 100644
--- a/db/helper/CliHelper.php
+++ b/db/helper/CliHelper.php
@@ -7,11 +7,10 @@
  * file that was distributed with this source code.
  */
 
-
 namespace dmstr\db\helper;
 
-
 use mikehaertl\shellcommand\Command;
+use yii\base\Exception;
 use yii\db\Connection;
 
 /**
@@ -24,9 +23,12 @@
  */
 class CliHelper
 {
+    public static function getMysqlCommand($mysqlExecutable = 'mysql', ?Connection $db = null)
+    {
+        if ($db === null) {
+            throw new Exception('Invalid database config');
+        }
 
-
-    public static function getMysqlCommand($mysqlExecutable = 'mysql', $db){
         $dsnOpts = CliHelper::getMysqlOptsFromDsn($db);
 
         $command = new Command($mysqlExecutable);
@@ -54,7 +56,7 @@ public static function getMysqlOptsFromDsn(Connection $db)
 
         $cliArgs = [
             'host' => null,
-            'db'   => null,
+            'db' => null,
             'port' => 3306,
         ];
 
@@ -101,4 +103,4 @@ public static function getMysqlCliArgsFromPdo(Connection $db)
         return $cliArgs;
     }
 
-}
\ No newline at end of file
+}