diff --git a/ipykernel/kernelbase.py b/ipykernel/kernelbase.py
index 4dcb5877..5acc7424 100644
--- a/ipykernel/kernelbase.py
+++ b/ipykernel/kernelbase.py
@@ -214,7 +214,9 @@ def _parent_header(self):
         "is_complete_request",
         "interrupt_request",
     ]
-    # add deprecated ipyparallel control messages
+
+    # control channel accepts all shell messages
+    # and some of its own
     control_msg_types = [
         *msg_types,
         "debug_request",