diff --git a/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/base.py b/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/base.py
index deaaeccf..cfede142 100644
--- a/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/base.py
+++ b/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/base.py
@@ -103,7 +103,7 @@ def __init__(
         scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
 
         # Save the scopes.
-        self._scopes = scopes or self.AUTH_SCOPES
+        self._scopes = scopes
 
         # If no credentials are provided, then determine the appropriate
         # defaults.
diff --git a/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc.py b/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc.py
index d778dc8f..3e0ac2fb 100644
--- a/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc.py
+++ b/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc.py
@@ -75,6 +75,7 @@ def __init__(
         client_cert_source_for_mtls: Callable[[], Tuple[bytes, bytes]] = None,
         quota_project_id: Optional[str] = None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
     ) -> None:
         """Instantiate the transport.
 
@@ -115,6 +116,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
 
         Raises:
           google.auth.exceptions.MutualTLSChannelError: If mutual TLS transport
@@ -167,7 +170,7 @@ def __init__(
             scopes=scopes,
             quota_project_id=quota_project_id,
             client_info=client_info,
-            always_use_jwt_access=True,
+            always_use_jwt_access=always_use_jwt_access,
         )
 
         if not self._grpc_channel:
diff --git a/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc_asyncio.py b/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc_asyncio.py
index 7e64f1c6..947ea80e 100644
--- a/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc_asyncio.py
+++ b/google/cloud/bigquery_reservation_v1/services/reservation_service/transports/grpc_asyncio.py
@@ -121,6 +121,7 @@ def __init__(
         client_cert_source_for_mtls: Callable[[], Tuple[bytes, bytes]] = None,
         quota_project_id=None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
     ) -> None:
         """Instantiate the transport.
 
@@ -162,6 +163,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
 
         Raises:
             google.auth.exceptions.MutualTlsChannelError: If mutual TLS transport
@@ -213,7 +216,7 @@ def __init__(
             scopes=scopes,
             quota_project_id=quota_project_id,
             client_info=client_info,
-            always_use_jwt_access=True,
+            always_use_jwt_access=always_use_jwt_access,
         )
 
         if not self._grpc_channel:
diff --git a/tests/unit/gapic/bigquery_reservation_v1/test_reservation_service.py b/tests/unit/gapic/bigquery_reservation_v1/test_reservation_service.py
index 3e0d353b..debc69d9 100644
--- a/tests/unit/gapic/bigquery_reservation_v1/test_reservation_service.py
+++ b/tests/unit/gapic/bigquery_reservation_v1/test_reservation_service.py
@@ -137,7 +137,25 @@ def test_reservation_service_client_service_account_always_use_jwt(client_class)
     ) as use_jwt:
         creds = service_account.Credentials(None, None, None)
         client = client_class(credentials=creds)
-        use_jwt.assert_called_with(True)
+        use_jwt.assert_not_called()
+
+
+@pytest.mark.parametrize(
+    "transport_class,transport_name",
+    [
+        (transports.ReservationServiceGrpcTransport, "grpc"),
+        (transports.ReservationServiceGrpcAsyncIOTransport, "grpc_asyncio"),
+    ],
+)
+def test_reservation_service_client_service_account_always_use_jwt_true(
+    transport_class, transport_name
+):
+    with mock.patch.object(
+        service_account.Credentials, "with_always_use_jwt_access", create=True
+    ) as use_jwt:
+        creds = service_account.Credentials(None, None, None)
+        transport = transport_class(credentials=creds, always_use_jwt_access=True)
+        use_jwt.assert_called_once_with(True)
 
 
 @pytest.mark.parametrize(
@@ -5902,10 +5920,7 @@ def test_reservation_service_grpc_transport_client_cert_source_for_mtls(
             "squid.clam.whelk:443",
             credentials=cred,
             credentials_file=None,
-            scopes=(
-                "https://www.googleapis.com/auth/bigquery",
-                "https://www.googleapis.com/auth/cloud-platform",
-            ),
+            scopes=None,
             ssl_credentials=mock_ssl_channel_creds,
             quota_project_id=None,
             options=[
@@ -6014,10 +6029,7 @@ def test_reservation_service_transport_channel_mtls_with_client_cert_source(
                 "mtls.squid.clam.whelk:443",
                 credentials=cred,
                 credentials_file=None,
-                scopes=(
-                    "https://www.googleapis.com/auth/bigquery",
-                    "https://www.googleapis.com/auth/cloud-platform",
-                ),
+                scopes=None,
                 ssl_credentials=mock_ssl_cred,
                 quota_project_id=None,
                 options=[
@@ -6064,10 +6076,7 @@ def test_reservation_service_transport_channel_mtls_with_adc(transport_class):
                 "mtls.squid.clam.whelk:443",
                 credentials=mock_cred,
                 credentials_file=None,
-                scopes=(
-                    "https://www.googleapis.com/auth/bigquery",
-                    "https://www.googleapis.com/auth/cloud-platform",
-                ),
+                scopes=None,
                 ssl_credentials=mock_ssl_cred,
                 quota_project_id=None,
                 options=[