diff --git a/Client/KeyUpgradeClient.php b/Client/KeyUpgradeClient.php
index 004ab78..93ce942 100644
--- a/Client/KeyUpgradeClient.php
+++ b/Client/KeyUpgradeClient.php
@@ -27,7 +27,7 @@ public function fetchPublicKeyId($merchantId, $accessKeyId, $secretKey, $newPubl
             'Timestamp' => date('Y-m-d\TH:i:s\Z'),
         ];
 
-        $parameters['Signature'] = $this->calculateSignature($parameters);
+        $parameters['Signature'] = $this->calculateSignature($parameters, $secretKey);
 
         $response = $this->curl->invokeCurl(
             'GET',
@@ -44,11 +44,11 @@ public function fetchPublicKeyId($merchantId, $accessKeyId, $secretKey, $newPubl
         return $responseData['publicKeyId'];
     }
 
-    public function calculateSignature($parameters)
+    public function calculateSignature($parameters, $secretKey)
     {
         $signingParameters = $parameters;
         unset($signingParameters['PublicKey']);
-        $signingParameters['SellerId'] = $signingParameters['MerchantId']);
+        $signingParameters['SellerId'] = $signingParameters['MerchantId'];
         unset($signingParameters['MerchantId']);
 
         ksort($signingParameters);
@@ -60,4 +60,4 @@ public function calculateSignature($parameters)
 
         return base64_encode(hash_hmac('sha256', $stringToSign, $secretKey, true));
     }
-}
\ No newline at end of file
+}