diff --git a/tests/system.py b/tests/system.py
index 188089d94..995b984ed 100644
--- a/tests/system.py
+++ b/tests/system.py
@@ -968,8 +968,8 @@ def _create_signed_read_url_helper(
             method=method,
             client=Config.CLIENT,
             version=version,
-            service_account_email=None,
-            access_token=None,
+            service_account_email=service_account_email,
+            access_token=access_token,
         )
 
         headers = {}
@@ -1046,7 +1046,10 @@ def test_create_signed_read_url_v2_w_access_token(self):
         client = iam_credentials_v1.IAMCredentialsClient()
         service_account_email = Config.CLIENT._credentials.service_account_email
         name = client.service_account_path("-", service_account_email)
-        scope = ["https://www.googleapis.com/auth/devstorage.read_write"]
+        scope = [
+            "https://www.googleapis.com/auth/devstorage.read_write",
+            "https://www.googleapis.com/auth/iam",
+        ]
         response = client.generate_access_token(name, scope)
         self._create_signed_read_url_helper(
             service_account_email=service_account_email,
@@ -1057,7 +1060,10 @@ def test_create_signed_read_url_v4_w_access_token(self):
         client = iam_credentials_v1.IAMCredentialsClient()
         service_account_email = Config.CLIENT._credentials.service_account_email
         name = client.service_account_path("-", service_account_email)
-        scope = ["https://www.googleapis.com/auth/devstorage.read_write"]
+        scope = [
+            "https://www.googleapis.com/auth/devstorage.read_write",
+            "https://www.googleapis.com/auth/iam",
+        ]
         response = client.generate_access_token(name, scope)
         self._create_signed_read_url_helper(
             version="v4",