diff --git a/src/main/java/org/casbin/casdoor/service/ProductService.java b/src/main/java/org/casbin/casdoor/service/ProductService.java
index 61ef797..ffa2e0c 100644
--- a/src/main/java/org/casbin/casdoor/service/ProductService.java
+++ b/src/main/java/org/casbin/casdoor/service/ProductService.java
@@ -56,10 +56,11 @@ public CasdoorResponse<String, Object> updateProduct(Product product) throws IOE
         return modifyProduct(ProductOperations.UPDATE_PRODUCT, product, null);
     }
 
-    public Product buyProduct(String name, String providerName) throws IOException {
+    public Product buyProduct(String name, String providerName, String userName) throws IOException {
         java.util.Map<String, String> queryMap = Map.of(
                 "id", config.organizationName + "/" + name,
-                "providerName", providerName
+                "providerName", providerName,
+                "userName", userName
         );
         CasdoorResponse<Product, Object> response = doPost("buy-product", queryMap, "", new TypeReference<CasdoorResponse<Product, Object>>() {
         });
diff --git a/src/test/java/org/casbin/casdoor/ProductTest.java b/src/test/java/org/casbin/casdoor/ProductTest.java
index e3d6a7f..6b80fbd 100644
--- a/src/test/java/org/casbin/casdoor/ProductTest.java
+++ b/src/test/java/org/casbin/casdoor/ProductTest.java
@@ -21,6 +21,7 @@
 
 import java.time.LocalDateTime;
 import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
 import java.util.List;
 
 import static org.junit.jupiter.api.Assertions.*;
@@ -47,6 +48,8 @@ public void testProduct() {
                 0,
                 "Published"
         );
+        product.providers = new ArrayList<>();
+        product.providers.add("provider_payment_dummy");
         assertDoesNotThrow(() -> productService.addProduct(product));
 
         // Get all objects, check if our added object is inside the list
@@ -89,7 +92,7 @@ public void testProduct() {
         // Test the buyProduct function
         Product boughtProduct;
         try {
-            boughtProduct = productService.buyProduct(name, "provider_payment_paypal");
+            boughtProduct = productService.buyProduct(name, "provider_payment_dummy", "admin");
         } catch (Exception e) {
             String errorMessage = e.getMessage();
             if (errorMessage.contains("The user") && errorMessage.contains("doesn't exist")) {