diff --git a/src/Sermepa/Tpv/Tpv.php b/src/Sermepa/Tpv/Tpv.php
index eb03763..0161b1e 100644
--- a/src/Sermepa/Tpv/Tpv.php
+++ b/src/Sermepa/Tpv/Tpv.php
@@ -875,7 +875,7 @@ public function check($key, $postData)
         $signatureReceived = $postData["Ds_Signature"];
         $signature = $this->generateMerchantSignatureNotification($key, $parameters);
 
-        return ($signature === $signatureReceived);
+        return hash_equals($signature, $signatureReceived);
     }
 
     /**