diff --git a/tc/obsw_tc_service23.py b/tc/obsw_tc_service23.py
index d0e09076441a3838e1db0e7958a7f3d2ec70863a..ff3e7460fa197b75de2fc1bdbfa85e20abdcd39c 100644
--- a/tc/obsw_tc_service23.py
+++ b/tc/obsw_tc_service23.py
@@ -41,7 +41,7 @@ class Service23WriteToFile:
         self.data_to_pack += bytearray(filename, 'utf-8')
         self.pus_packets = self.split_large_file(size_of_data_blocks)
 
-    def split_large_file(self, size_of_data_blocks):
+    def split_large_file(self, size_of_data_blocks: int):
         """ This function splits a large file in multiple packets
             This is necessary because the packet size is limited