diff --git a/nvflare/fuel/hci/chunk.py b/nvflare/fuel/hci/chunk.py
index 0c25eb82af..e4b01e0acb 100644
--- a/nvflare/fuel/hci/chunk.py
+++ b/nvflare/fuel/hci/chunk.py
@@ -56,7 +56,7 @@ def __str__(self):
     @classmethod
     def from_bytes(cls, buffer: bytes):
         if len(buffer) < HEADER_LEN:
-            raise ValueError(f"Prefix too short")
+            raise ValueError("Prefix too short")
 
         marker, num1, num2 = HEADER_STRUCT.unpack_from(buffer, 0)
         return Header(marker, num1, num2)
diff --git a/nvflare/fuel/hci/client/file_transfer.py b/nvflare/fuel/hci/client/file_transfer.py
index ecddcd8426..d5c5ad0533 100644
--- a/nvflare/fuel/hci/client/file_transfer.py
+++ b/nvflare/fuel/hci/client/file_transfer.py
@@ -31,7 +31,6 @@
 from nvflare.lighter.utils import load_private_key_file, sign_folders
 from nvflare.security.logging import secure_format_exception, secure_log_traceback
 
-from ..proto import MetaKey
 from .api_spec import CommandContext, ReplyProcessor
 from .api_status import APIStatus
 
diff --git a/nvflare/private/fed/server/job_runner.py b/nvflare/private/fed/server/job_runner.py
index ebeec51bc1..0d733db22a 100644
--- a/nvflare/private/fed/server/job_runner.py
+++ b/nvflare/private/fed/server/job_runner.py
@@ -29,7 +29,7 @@
 from nvflare.apis.job_scheduler_spec import DispatchInfo
 from nvflare.apis.workspace import Workspace
 from nvflare.fuel.utils.argument_utils import parse_vars
-from nvflare.fuel.utils.zip_utils import zip_directory_to_bytes, zip_directory_to_file
+from nvflare.fuel.utils.zip_utils import zip_directory_to_file
 from nvflare.lighter.utils import verify_folder_signature
 from nvflare.private.admin_defs import Message, MsgHeader, ReturnCode
 from nvflare.private.defs import RequestHeader, TrainingTopic