diff --git a/phpstan.neon b/phpstan.neon
index dcfd312..2c1409d 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,7 +1,7 @@
 includes:
 	- phpstan-baseline.neon
 parameters:
-    level: 6
+    level: 8
     paths:
         - src
     bootstrapFiles:
diff --git a/src/QueryBuilderForm.php b/src/QueryBuilderForm.php
index 4713201..c26fd73 100644
--- a/src/QueryBuilderForm.php
+++ b/src/QueryBuilderForm.php
@@ -99,10 +99,11 @@ class QueryBuilderForm extends Widget
     public function init() : void
     {
         if (is_array($this->builder)) {
-            $this->builder = Yii::createObject(array_merge([
-                    'class' => QueryBuilder::className()
-                ], $this->builder)
-            );
+            /** @var QueryBuilder $builder */
+            $builder = Yii::createObject(array_merge([
+                'class' => QueryBuilder::class
+            ], $this->builder));
+            $this->builder = $builder;
         }
 
         if (!$this->builder instanceof QueryBuilder) {
@@ -125,7 +126,11 @@ public function run()
     {
         echo Html::endForm();
 
+        /** @var string $id */
         $id = $this->options['id'];
+        if(!$this->builder instanceof QueryBuilder) {
+            throw new InvalidConfigException("Builder needs to be builder object");
+        }
         $builderId = $this->builder->getId();
         $view = $this->getView();
 
diff --git a/src/Translator.php b/src/Translator.php
index d665af5..59c12c9 100644
--- a/src/Translator.php
+++ b/src/Translator.php
@@ -99,11 +99,11 @@ public function init() : void
     /**
      * Encodes filter rule into SQL condition
      * @param string $field field name
-     * @param string|array<mixed> $type operator type
-     * @param string|array<string, mixed> $params query parameters
+     * @param string $type operator type
+     * @param array<string, mixed> $params query parameters
      * @return string encoded rule
      */
-    protected function encodeRule($field, $type, $params)
+    protected function encodeRule(string $field, string $type, array $params)
     {
         $pattern = $this->_operators[$type];
         $keys = array_keys($params);