diff --git a/ipykernel/kernelbase.py b/ipykernel/kernelbase.py
index a6451bebb..56fea46c2 100644
--- a/ipykernel/kernelbase.py
+++ b/ipykernel/kernelbase.py
@@ -257,14 +257,14 @@ async def _flush_control_queue(self):
             control_loop = self.io_loop
             tracer_future = awaitable_future = asyncio.Future()
 
-        def _flush():
+        async def _flush():
             # control_stream.flush puts messages on the queue
             self.control_stream.flush()
             # put Future on the queue after all of those,
             # so we can wait for all queued messages to be processed
-            self.control_queue.put(tracer_future)
+            await self.control_queue.put(tracer_future)
 
-        control_loop.call_soon_threadsafe(_flush)
+        asyncio.run_coroutine_threadsafe(_flush(), control_loop)
         return awaitable_future
 
     async def process_control(self, msg):