diff --git a/src/pyob/entrance_mixins.py b/src/pyob/entrance_mixins.py
index 6223930..c74bab7 100644
--- a/src/pyob/entrance_mixins.py
+++ b/src/pyob/entrance_mixins.py
@@ -110,7 +110,7 @@ def start_dashboard(self):
         # 2. Initialize and Start the Live Server
 
         # Dynamically add do_POST method for manual target handling
-        def _dynamic_do_POST_method(handler_instance: ObserverHandler):
+        def _dynamic_do_POST_method(handler_instance: ObserverHandler) -> None:
             if handler_instance.path == "/set_target":
                 try:
                     content_length = int(