diff --git a/google/cloud/functions_v1/services/cloud_functions_service/async_client.py b/google/cloud/functions_v1/services/cloud_functions_service/async_client.py
index be8ff34..36fd704 100644
--- a/google/cloud/functions_v1/services/cloud_functions_service/async_client.py
+++ b/google/cloud/functions_v1/services/cloud_functions_service/async_client.py
@@ -332,7 +332,7 @@ async def get_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([name])
         if request is not None and has_flattened_params:
@@ -425,7 +425,7 @@ async def create_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([location, function])
         if request is not None and has_flattened_params:
@@ -509,7 +509,7 @@ async def update_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([function])
         if request is not None and has_flattened_params:
@@ -616,7 +616,7 @@ async def delete_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([name])
         if request is not None and has_flattened_params:
@@ -714,7 +714,7 @@ async def call_function(
                 Response of CallFunction method.
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([name, data])
         if request is not None and has_flattened_params:
@@ -839,8 +839,7 @@ async def generate_download_url(
         limited period and should be used within minutes after
         generation.
         For more information about the signed URL usage see:
-        https://cloud.google.com/storage/docs/access-
-        control/signed-urls
+        https://cloud.google.com/storage/docs/access-control/signed-urls
 
         Args:
             request (Union[google.cloud.functions_v1.types.GenerateDownloadUrlRequest, dict]):
diff --git a/google/cloud/functions_v1/services/cloud_functions_service/client.py b/google/cloud/functions_v1/services/cloud_functions_service/client.py
index 1b01aba..ff806df 100644
--- a/google/cloud/functions_v1/services/cloud_functions_service/client.py
+++ b/google/cloud/functions_v1/services/cloud_functions_service/client.py
@@ -546,7 +546,7 @@ def get_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([name])
         if request is not None and has_flattened_params:
@@ -629,7 +629,7 @@ def create_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([location, function])
         if request is not None and has_flattened_params:
@@ -713,7 +713,7 @@ def update_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([function])
         if request is not None and has_flattened_params:
@@ -810,7 +810,7 @@ def delete_function(
 
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([name])
         if request is not None and has_flattened_params:
@@ -898,7 +898,7 @@ def call_function(
                 Response of CallFunction method.
         """
         # Create or coerce a protobuf request object.
-        # Sanity check: If we got a request object, we should *not* have
+        # Quick check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
         has_flattened_params = any([name, data])
         if request is not None and has_flattened_params:
@@ -1024,8 +1024,7 @@ def generate_download_url(
         limited period and should be used within minutes after
         generation.
         For more information about the signed URL usage see:
-        https://cloud.google.com/storage/docs/access-
-        control/signed-urls
+        https://cloud.google.com/storage/docs/access-control/signed-urls
 
         Args:
             request (Union[google.cloud.functions_v1.types.GenerateDownloadUrlRequest, dict]):
diff --git a/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc.py b/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc.py
index d2dcbd9..74f4250 100644
--- a/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc.py
+++ b/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc.py
@@ -164,8 +164,11 @@ def __init__(
         if not self._grpc_channel:
             self._grpc_channel = type(self).create_channel(
                 self._host,
+                # use the credentials which are saved
                 credentials=self._credentials,
-                credentials_file=credentials_file,
+                # Set ``credentials_file`` to ``None`` here as
+                # the credentials that we saved earlier should be used.
+                credentials_file=None,
                 scopes=self._scopes,
                 ssl_credentials=self._ssl_channel_credentials,
                 quota_project_id=quota_project_id,
@@ -238,7 +241,7 @@ def operations_client(self) -> operations_v1.OperationsClient:
         This property caches on the instance; repeated calls return the same
         client.
         """
-        # Sanity check: Only create a new client if we do not already have one.
+        # Quick check: Only create a new client if we do not already have one.
         if self._operations_client is None:
             self._operations_client = operations_v1.OperationsClient(self.grpc_channel)
 
@@ -479,8 +482,7 @@ def generate_download_url(
         limited period and should be used within minutes after
         generation.
         For more information about the signed URL usage see:
-        https://cloud.google.com/storage/docs/access-
-        control/signed-urls
+        https://cloud.google.com/storage/docs/access-control/signed-urls
 
         Returns:
             Callable[[~.GenerateDownloadUrlRequest],
diff --git a/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc_asyncio.py b/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc_asyncio.py
index a0a7976..f6fbcee 100644
--- a/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc_asyncio.py
+++ b/google/cloud/functions_v1/services/cloud_functions_service/transports/grpc_asyncio.py
@@ -209,8 +209,11 @@ def __init__(
         if not self._grpc_channel:
             self._grpc_channel = type(self).create_channel(
                 self._host,
+                # use the credentials which are saved
                 credentials=self._credentials,
-                credentials_file=credentials_file,
+                # Set ``credentials_file`` to ``None`` here as
+                # the credentials that we saved earlier should be used.
+                credentials_file=None,
                 scopes=self._scopes,
                 ssl_credentials=self._ssl_channel_credentials,
                 quota_project_id=quota_project_id,
@@ -240,7 +243,7 @@ def operations_client(self) -> operations_v1.OperationsAsyncClient:
         This property caches on the instance; repeated calls return the same
         client.
         """
-        # Sanity check: Only create a new client if we do not already have one.
+        # Quick check: Only create a new client if we do not already have one.
         if self._operations_client is None:
             self._operations_client = operations_v1.OperationsAsyncClient(
                 self.grpc_channel
@@ -495,8 +498,7 @@ def generate_download_url(
         limited period and should be used within minutes after
         generation.
         For more information about the signed URL usage see:
-        https://cloud.google.com/storage/docs/access-
-        control/signed-urls
+        https://cloud.google.com/storage/docs/access-control/signed-urls
 
         Returns:
             Callable[[~.GenerateDownloadUrlRequest],
diff --git a/tests/unit/gapic/functions_v1/test_cloud_functions_service.py b/tests/unit/gapic/functions_v1/test_cloud_functions_service.py
index 9b6ab47..6abfc8f 100644
--- a/tests/unit/gapic/functions_v1/test_cloud_functions_service.py
+++ b/tests/unit/gapic/functions_v1/test_cloud_functions_service.py
@@ -29,6 +29,7 @@
 from google.api_core import gapic_v1
 from google.api_core import grpc_helpers
 from google.api_core import grpc_helpers_async
+from google.api_core import operation
 from google.api_core import operation_async  # type: ignore
 from google.api_core import operations_v1
 from google.api_core import path_template
@@ -543,25 +544,28 @@ def test_cloud_functions_service_client_client_options_scopes(
 
 
 @pytest.mark.parametrize(
-    "client_class,transport_class,transport_name",
+    "client_class,transport_class,transport_name,grpc_helpers",
     [
         (
             CloudFunctionsServiceClient,
             transports.CloudFunctionsServiceGrpcTransport,
             "grpc",
+            grpc_helpers,
         ),
         (
             CloudFunctionsServiceAsyncClient,
             transports.CloudFunctionsServiceGrpcAsyncIOTransport,
             "grpc_asyncio",
+            grpc_helpers_async,
         ),
     ],
 )
 def test_cloud_functions_service_client_client_options_credentials_file(
-    client_class, transport_class, transport_name
+    client_class, transport_class, transport_name, grpc_helpers
 ):
     # Check the case credentials file is provided.
     options = client_options.ClientOptions(credentials_file="credentials.json")
+
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
         client = client_class(client_options=options, transport=transport_name)
@@ -597,6 +601,72 @@ def test_cloud_functions_service_client_client_options_from_dict():
         )
 
 
+@pytest.mark.parametrize(
+    "client_class,transport_class,transport_name,grpc_helpers",
+    [
+        (
+            CloudFunctionsServiceClient,
+            transports.CloudFunctionsServiceGrpcTransport,
+            "grpc",
+            grpc_helpers,
+        ),
+        (
+            CloudFunctionsServiceAsyncClient,
+            transports.CloudFunctionsServiceGrpcAsyncIOTransport,
+            "grpc_asyncio",
+            grpc_helpers_async,
+        ),
+    ],
+)
+def test_cloud_functions_service_client_create_channel_credentials_file(
+    client_class, transport_class, transport_name, grpc_helpers
+):
+    # Check the case credentials file is provided.
+    options = client_options.ClientOptions(credentials_file="credentials.json")
+
+    with mock.patch.object(transport_class, "__init__") as patched:
+        patched.return_value = None
+        client = client_class(client_options=options, transport=transport_name)
+        patched.assert_called_once_with(
+            credentials=None,
+            credentials_file="credentials.json",
+            host=client.DEFAULT_ENDPOINT,
+            scopes=None,
+            client_cert_source_for_mtls=None,
+            quota_project_id=None,
+            client_info=transports.base.DEFAULT_CLIENT_INFO,
+            always_use_jwt_access=True,
+        )
+
+    # test that the credentials from file are saved and used as the credentials.
+    with mock.patch.object(
+        google.auth, "load_credentials_from_file", autospec=True
+    ) as load_creds, mock.patch.object(
+        google.auth, "default", autospec=True
+    ) as adc, mock.patch.object(
+        grpc_helpers, "create_channel"
+    ) as create_channel:
+        creds = ga_credentials.AnonymousCredentials()
+        file_creds = ga_credentials.AnonymousCredentials()
+        load_creds.return_value = (file_creds, None)
+        adc.return_value = (creds, None)
+        client = client_class(client_options=options, transport=transport_name)
+        create_channel.assert_called_with(
+            "cloudfunctions.googleapis.com:443",
+            credentials=file_creds,
+            credentials_file=None,
+            quota_project_id=None,
+            default_scopes=("https://www.googleapis.com/auth/cloud-platform",),
+            scopes=None,
+            default_host="cloudfunctions.googleapis.com",
+            ssl_credentials=None,
+            options=[
+                ("grpc.max_send_message_length", -1),
+                ("grpc.max_receive_message_length", -1),
+            ],
+        )
+
+
 @pytest.mark.parametrize("request_type", [functions.ListFunctionsRequest, dict,])
 def test_list_functions(request_type, transport: str = "grpc"):
     client = CloudFunctionsServiceClient(