diff --git a/src/Configuration/ConfigMerger.php b/src/Configuration/ConfigMerger.php
new file mode 100644
index 00000000000..16bb4335867
--- /dev/null
+++ b/src/Configuration/ConfigMerger.php
@@ -0,0 +1,37 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Configuration;
+
+final class ConfigMerger
+{
+    /**
+     * @todo resolve nicely, memory leak at the moment: https://travis-ci.org/rectorphp/rector/jobs/319947148#L641
+     *
+     * This magic will merge array recursively without making any extra duplications.
+     *
+     * Only array_merge doesn't work in this case.
+     *
+     * @param mixed[] $configs
+     * @return mixed[]
+     */
+    public function mergeConfigs(array $configs): array
+    {
+        dump($configs);
+
+        if (count($configs) <= 1) {
+            return $configs[0];
+        }
+
+        $mergedConfigs = [];
+
+        foreach ($configs as $config) {
+            $mergedConfigs = array_merge(
+                $mergedConfigs,
+                $config,
+                array_replace_recursive($mergedConfigs, $config)
+            );
+        }
+
+        return $mergedConfigs;
+    }
+}
diff --git a/src/DependencyInjection/Extension/RectorsExtension.php b/src/DependencyInjection/Extension/RectorsExtension.php
index 78d22cea9f4..c7c103932ac 100644
--- a/src/DependencyInjection/Extension/RectorsExtension.php
+++ b/src/DependencyInjection/Extension/RectorsExtension.php
@@ -2,6 +2,7 @@
 
 namespace Rector\DependencyInjection\Extension;
 
+use Rector\Configuration\ConfigMerger;
 use Rector\Configuration\Normalizer\RectorClassNormalizer;
 use Rector\Configuration\Validator\RectorClassValidator;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
@@ -19,12 +20,19 @@ final class RectorsExtension extends Extension
      */
     private $rectorClassNormalizer;
 
+    /**
+     * @var ConfigMerger
+     */
+    private $configMerger;
+
     public function __construct(
         RectorClassValidator $rectorClassValidator,
-        RectorClassNormalizer $rectorClassNormalizer
+        RectorClassNormalizer $rectorClassNormalizer,
+        ConfigMerger $configurationMerger
     ) {
         $this->rectorClassValidator = $rectorClassValidator;
         $this->rectorClassNormalizer = $rectorClassNormalizer;
+        $this->configMerger = $configurationMerger;
     }
 
     /**
@@ -36,43 +44,18 @@ final class RectorsExtension extends Extension
             return;
         }
 
-        $rectors = $this->mergeAllConfigsRecursively($configs);
-
+        $rectors = $this->configMerger->mergeConfigs($configs);
         $rectors = $this->rectorClassNormalizer->normalize($rectors);
 
         $this->rectorClassValidator->validate(array_keys($rectors));
 
         foreach ($rectors as $rectorClass => $arguments) {
             $rectorDefinition = $containerBuilder->autowire($rectorClass);
-            if (! count($arguments)) {
+            if (! $arguments) {
                 continue;
             }
 
             $rectorDefinition->setArguments([$arguments]);
         }
     }
-
-    /**
-     * This magic will merge array recursively
-     * without making any extra duplications.
-     *
-     * Only array_merge doesn't work in this case.
-     *
-     * @param mixed[] $configs
-     * @return mixed[]
-     */
-    private function mergeAllConfigsRecursively(array $configs): array
-    {
-        $mergedConfigs = [];
-
-        foreach ($configs as $config) {
-            $mergedConfigs = array_merge(
-                $mergedConfigs,
-                $config,
-                array_replace_recursive($mergedConfigs, $config)
-            );
-        }
-
-        return $mergedConfigs;
-    }
 }
diff --git a/src/DependencyInjection/RectorBundle.php b/src/DependencyInjection/RectorBundle.php
index f4c250460dd..fbdd3601dec 100644
--- a/src/DependencyInjection/RectorBundle.php
+++ b/src/DependencyInjection/RectorBundle.php
@@ -2,6 +2,7 @@
 
 namespace Rector\DependencyInjection;
 
+use Rector\Configuration\ConfigMerger;
 use Rector\Configuration\Normalizer\RectorClassNormalizer;
 use Rector\Configuration\Validator\RectorClassValidator;
 use Rector\DependencyInjection\Extension\RectorsExtension;
@@ -11,9 +12,6 @@ final class RectorBundle extends Bundle
 {
     public function getContainerExtension(): RectorsExtension
     {
-        return new RectorsExtension(
-            new RectorClassValidator(),
-            new RectorClassNormalizer()
-        );
+        return new RectorsExtension(new RectorClassValidator(), new RectorClassNormalizer(), new ConfigMerger());
     }
 }
diff --git a/tests/Configuration/ConfigMergerTest.php b/tests/Configuration/ConfigMergerTest.php
new file mode 100644
index 00000000000..37ff3974e69
--- /dev/null
+++ b/tests/Configuration/ConfigMergerTest.php
@@ -0,0 +1,37 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Tests\Configuration;
+
+use PHPUnit\Framework\TestCase;
+use Rector\Configuration\ConfigMerger;
+
+final class ConfigMergerTest extends TestCase
+{
+    /**
+     * @var ConfigMerger
+     */
+    private $configMerger;
+
+    protected function setUp(): void
+    {
+        $this->configMerger = new ConfigMerger();
+    }
+
+    public function test(): void
+    {
+        $result = $this->configMerger->mergeConfigs([
+            ['SomeRector' => ['key' => 'value']]
+        ]);
+
+        $this->assertSame(['SomeRector' => ['key' => 'value']], $result);
+
+        $result = $this->configMerger->mergeConfigs([
+            ['SomeRector' => ['key' => ['value']]],
+            ['SomeRector' => ['key' => ['another_value']]]
+        ]);
+
+        $this->assertSame(['SomeRector' => ['key' => 'value']], $result);
+
+    }
+}
+