diff --git a/Merchant.php b/Merchant.php
index a63e267..ad89ca3 100644
--- a/Merchant.php
+++ b/Merchant.php
@@ -39,7 +39,7 @@ public function payment($nOutSum, $nInvId, $sInvDesc = null, $sIncCurrLabel = nu
     {
         $url = $this->baseUrl;
 
-        $sSignatureValue = $this->generateSignature($nOutSum, $nInvId);
+        $sSignatureValue = $this->generateSignature($nOutSum, $nInvId, $shp);
 
         $url .= '?' . http_build_query([
                 'MrchLogin' => $this->sMerchantLogin,
@@ -80,7 +80,7 @@ private function implodeShp($shp)
         return implode(':', $shp);
     }
 
-    private function generateSignature($nOutSum, $nInvId)
+    private function generateSignature($nOutSum, $nInvId, $shp = [])
     {
         if ($nInvId === null) {
             // MerchantLogin:OutSum:Пароль#1
@@ -90,6 +90,10 @@ private function generateSignature($nOutSum, $nInvId)
             $signature = "{$this->sMerchantLogin}:{$nOutSum}:{$nInvId}:{$this->sMerchantPass1}";
         }
 
+        if (!empty($shp)) {
+            $signature .= ':' . $this->implodeShp($shp);
+        }
+
         return strtolower($this->encryptSignature($signature));
     }
 
diff --git a/tests/unit/MerchantTest.php b/tests/unit/MerchantTest.php
index 0eb0615..45725d2 100644
--- a/tests/unit/MerchantTest.php
+++ b/tests/unit/MerchantTest.php
@@ -67,9 +67,11 @@ public function testRedirectUrlUserParams()
             'shp_login' => 'user1',
         ];
 
+        $signatureHash = md5('demo:100:1:password_1:shp_id=1:shp_login=user1');
+
         $returnUrl = $merchant->payment(100, 1, 'Description', null, null, 'en', $userParams, true);
 
-        $this->assertEquals("https://auth.robokassa.ru/Merchant/Index.aspx?MrchLogin=demo&OutSum=100&InvId=1&Desc=Description&SignatureValue=8a50b8d86ed28921edfc371cff6e156f&Culture=en&IsTest=1&shp_id=1&shp_login=user1", $returnUrl);
+        $this->assertEquals("https://auth.robokassa.ru/Merchant/Index.aspx?MrchLogin=demo&OutSum=100&InvId=1&Desc=Description&SignatureValue={$signatureHash}&Culture=en&IsTest=1&shp_id=1&shp_login=user1", $returnUrl);
     }
 
     public function testResponseRedirect()