diff --git a/tc/obsw_tc_service23.py b/tc/obsw_tc_service23.py
index e4a23407b8f6df9674e1ab1bf1cab8f9646d9999..9fb986204fce192a1e59208990bd741d4bc3cf60 100644
--- a/tc/obsw_tc_service23.py
+++ b/tc/obsw_tc_service23.py
@@ -162,11 +162,11 @@ class FileTransferHelper:
         @param init_ssc: The ssc of the first command, will be incremented by one for each packet.
         """
         number_of_packets = math.floor(len(data) / size_of_data_blocks)
-        packet_number = 0
+        packet_sequence_number = 0
 
         for i in range(number_of_packets):
-            header.append(packet_number >> 8)
-            header.append(0xFF & packet_number)
+            header.append(packet_sequence_number >> 8)
+            header.append(0xFF & packet_sequence_number)
             header += data[i * size_of_data_blocks:(i + 1) * size_of_data_blocks]
 
             commands = PusTelecommand(service=23, subservice=128, ssc=init_ssc + i,
@@ -175,23 +175,23 @@ class FileTransferHelper:
 
             # Remove everything except the header
             header = header[:len(header) - size_of_data_blocks - 2]
-            packet_number = packet_number + 1
-        header.append(packet_number >> 8)
-        header.append(0xFF & packet_number)
+            packet_sequence_number = packet_sequence_number + 1
+        header.append(packet_sequence_number >> 8)
+        header.append(0xFF & packet_sequence_number)
         header += data[number_of_packets * size_of_data_blocks:len(data)]
-        commands = PusTelecommand(service=23, subservice=128, ssc=init_ssc + packet_number,
+        commands = PusTelecommand(service=23, subservice=128, ssc=init_ssc + packet_sequence_number,
                                   app_data=header)
         self.tc_queue.appendleft(commands.pack_command_tuple())
 
 
 def generate_create_file_srv23_1_packet(
         filename: str, repository_path: str, ssc: int, max_size_of_app_data: int,
-        initial_data=bytearray([]), object_id=g.SD_CARD_HANDLER_ID):
+        initial_data: bytearray = bytearray([]), object_id: bytearray = g.SD_CARD_HANDLER_ID):
     if len(initial_data) > calculate_allowed_file_data_size(
             max_size_of_app_data, filename, repository_path):
         LOGGER.error("generate_create_file_srv23_1_packet: Initial data too large!")
         return None
-    data_to_pack = object_id
+    data_to_pack = bytearray(object_id)
     data_to_pack += bytearray(repository_path, 'utf-8')
     # Add string terminator to repository_path
     data_to_pack.append(0)
@@ -214,7 +214,7 @@ def generate_rm_file_srv23_2_packet(filename: str, repository_path: str,
     @param object_id: The object ID of the memory handler which manages the file system
     :return The TC[23,2] PUS packet
     """
-    data_to_pack = object_id
+    data_to_pack = bytearray(object_id)
     data_to_pack += bytearray(repository_path, 'utf-8')
     # Add string terminator to repository_path
     data_to_pack.append(0)
@@ -225,7 +225,7 @@ def generate_rm_file_srv23_2_packet(filename: str, repository_path: str,
 
 
 def generate_mkdir_srv23_9_packet(directory_name: str, ssc: int, repository_path: str = "/",
-                                  object_id=g.SD_CARD_HANDLER_ID):
+                                  object_id: bytearray = g.SD_CARD_HANDLER_ID):
     """
     This function generates a packet which is used to create directories on file systems.
     @param directory_name: The path where the directory shall be created
@@ -234,7 +234,7 @@ def generate_mkdir_srv23_9_packet(directory_name: str, ssc: int, repository_path
     @param object_id: The object ID of the memory handler which manages the file system
     :return
     """
-    data_to_pack = object_id
+    data_to_pack = bytearray(object_id)
     data_to_pack += bytearray(repository_path, 'utf-8')
     # Add string terminator to repository path
     data_to_pack.append(0)
@@ -245,7 +245,7 @@ def generate_mkdir_srv23_9_packet(directory_name: str, ssc: int, repository_path
 
 
 def generate_rmdir_srv23_10_packet(directory_name: str, repository_path: str, ssc: int,
-                                   object_id=g.SD_CARD_HANDLER_ID):
+                                   object_id: bytearray = g.SD_CARD_HANDLER_ID):
     """
     This function generates a packet which deletes the a directory at the specified repository path.
     @param directory_name: Name of the directory to delete
@@ -254,7 +254,7 @@ def generate_rmdir_srv23_10_packet(directory_name: str, repository_path: str, ss
     @param object_id: object ID of the memory handler (e.g. SD Card Handler)
     @return The application data field of the (23,10) PUS packet
     """
-    data_to_pack = object_id
+    data_to_pack = bytearray(object_id)
     data_to_pack += bytearray(repository_path, 'utf-8')
     # Add string terminator of repository path
     data_to_pack.append(0)
@@ -265,9 +265,10 @@ def generate_rmdir_srv23_10_packet(directory_name: str, repository_path: str, ss
 
 
 def generate_append_to_file_srv23_128_packet(
-        filename: str, repository_path: str, ssc: int, file_data: bytearray = bytearray([]),
-        object_id=g.SD_CARD_HANDLER_ID):
-    data_to_pack = object_id
+        filename: str, repository_path: str, packet_sequence_number: int,
+        ssc: int, file_data: bytearray = bytearray([]),
+        object_id: bytearray = g.SD_CARD_HANDLER_ID):
+    data_to_pack = bytearray(object_id)
     data_to_pack += bytearray(repository_path, 'utf-8')
     # Add string terminator of repository path
     data_to_pack.append(0)
@@ -275,6 +276,8 @@ def generate_append_to_file_srv23_128_packet(
     # Add string terminator of filename
     data_to_pack.append(0)
     data_to_pack += file_data
+    data_to_pack.append(packet_sequence_number >> 8)
+    data_to_pack.append(packet_sequence_number & 0xff)
     return PusTelecommand(service=23, subservice=128, ssc=ssc, app_data=data_to_pack)
 
 
@@ -289,7 +292,7 @@ def generate_read_file_srv23_129_packet(repository_path: str, filename: str, ssc
     @param object_id: object ID of the memory handler (e.g. SD Card Handler)
     @return: The application data field of the (23,129) PUS packet
     """
-    data_to_pack = object_id
+    data_to_pack = bytearray(object_id)
     data_to_pack += bytearray(repository_path, 'utf-8')
     # Add string terminator of repository paht
     data_to_pack.append(0)
@@ -307,13 +310,14 @@ def pack_service23_test_into(tc_queue: Deque) -> Deque:
     tc_queue.appendleft(command.pack_command_tuple())
     tc_queue.append(("print", "Create subdirectory 'subdir' in 'test'"))
     command = generate_mkdir_srv23_9_packet(repository_path="test", ssc=2301,
-                                             directory_name="subdir")
+                                            directory_name="subdir")
     tc_queue.appendleft(command.pack_command_tuple())
 
     tc_queue.appendleft(("print", "Create test.bin"))
     command = generate_create_file_srv23_1_packet(
-         filename="test.bin", repository_path="test/subdir", ssc=2302,
-         initial_data=bytearray([0x01, 0x00, 0x01, 0x00]), max_size_of_app_data=1024)
+        filename="test.bin", repository_path="test/subdir", ssc=2302,
+        initial_data=bytearray([0x01, 0x00, 0x01, 0x00]),
+        max_size_of_app_data=1024)
     tc_queue.appendleft(command.pack_command_tuple())
     # tc_queue.appendleft(("print", "Read data of test.bin"))
     # command = generate_service23_subservice129_packet("test/subdir", "test.bin", sd_handler_id)