diff --git a/nextline/plugin/plugins/session/session.py b/nextline/plugin/plugins/session/session.py
index f09177b9..a2dd85bf 100644
--- a/nextline/plugin/plugins/session/session.py
+++ b/nextline/plugin/plugins/session/session.py
@@ -1,7 +1,6 @@
 import asyncio
 import contextlib
 import multiprocessing as mp
-import time
 from collections.abc import AsyncIterator, Callable
 from functools import partial
 from logging import getLogger
@@ -13,7 +12,7 @@
 from nextline import spawned
 from nextline.plugin.spec import Context, hookimpl
 from nextline.spawned import Command, QueueIn, QueueOut, RunResult
-from nextline.utils import run_in_process
+from nextline.utils import Timer, run_in_process
 
 pickling_support.install()
 
@@ -63,20 +62,25 @@ async def relay_events(context: Context, queue: QueueOut) -> AsyncIterator[None]
     '''Call the hook `on_event_in_process()` on events emitted in the spawned process.'''
     logger = getLogger(__name__)
 
+    in_finally = False
+    timer = Timer(timeout=1)  # seconds
+
     async def _monitor() -> None:
         while (event := await asyncio.to_thread(queue.get)) is not None:
             logger.debug(f'event: {event!r}')
             await context.hook.ahook.on_event_in_process(context=context, event=event)
+            if in_finally:
+                timer.restart()
 
     task = asyncio.create_task(_monitor())
     try:
         yield
     finally:
-        up_to = 0.05
-        start = time.process_time()
+        in_finally = True
+        timer.restart()
         while not queue.empty():
-            await asyncio.sleep(0)
-            if time.process_time() - start > up_to:
+            await asyncio.sleep(0)  # let _monitor() run
+            if timer.is_timeout():
                 logger.warning(f'Timeout. the queue is not empty: {queue!r}')
                 break
         await asyncio.to_thread(queue.put, None)  # type: ignore
diff --git a/nextline/spawned/__init__.py b/nextline/spawned/__init__.py
index 048a164a..5b31e3f6 100644
--- a/nextline/spawned/__init__.py
+++ b/nextline/spawned/__init__.py
@@ -25,6 +25,8 @@
 
 import traceback
 
+from nextline.utils import wait_until_queue_empty
+
 from .commands import Command, PdbCommand
 from .runner import run
 from .types import QueueIn, QueueOut, RunArg, RunResult, Statement
@@ -45,7 +47,9 @@ def main(run_arg: RunArg) -> RunResult:
     assert _queue_in
     assert _queue_out
     try:
-        return run(run_arg, _queue_in, _queue_out)
+        ret = run(run_arg, _queue_in, _queue_out)
+        wait_until_queue_empty(queue=_queue_out)
+        return ret
     except BaseException:
         traceback.print_exc()
         raise
diff --git a/nextline/utils/__init__.py b/nextline/utils/__init__.py
index 47bed802..14daecd0 100644
--- a/nextline/utils/__init__.py
+++ b/nextline/utils/__init__.py
@@ -13,11 +13,13 @@
     'profile_func',
     'PubSub',
     'PubSubItem',
+    'wait_until_queue_empty',
     'ExitedProcess',
     'RunningProcess',
     'run_in_process',
     'ExcThread',
     'ThreadTaskIdComposer',
+    'Timer',
 ]
 
 from .done_callback import TaskDoneCallback, ThreadDoneCallback, ThreadTaskDoneCallback
@@ -27,6 +29,8 @@
 from .peek import peek_stderr, peek_stdout, peek_textio
 from .profile import profile_func
 from .pubsub import PubSub, PubSubItem
+from .queue import wait_until_queue_empty
 from .run import ExitedProcess, RunningProcess, run_in_process
 from .thread_exception import ExcThread
 from .thread_task_id import ThreadTaskIdComposer
+from .timer import Timer
diff --git a/nextline/utils/queue.py b/nextline/utils/queue.py
new file mode 100644
index 00000000..0affd87f
--- /dev/null
+++ b/nextline/utils/queue.py
@@ -0,0 +1,31 @@
+import time
+from queue import Queue
+from typing import Optional
+
+from .timer import Timer
+
+
+def wait_until_queue_empty(
+    queue: Queue, timeout: Optional[float] = None, interval: float = 0.001
+) -> None:
+    '''Wait until the queue is empty.
+
+    Parameters
+    ----------
+    queue :
+        The queue to wait for.
+    timeout : optional
+        The timeout in seconds. Wait indefinitely if None.
+    interval : float, optional
+        The interval in seconds to check the queue.
+
+    '''
+    if timeout is None:
+        while not queue.empty():
+            time.sleep(interval)
+    else:
+        timer = Timer(timeout)
+        while not queue.empty():
+            if timer.is_timeout():
+                raise TimeoutError(f'Timeout. the queue is not empty: {queue!r}')
+            time.sleep(interval)
diff --git a/nextline/utils/timer.py b/nextline/utils/timer.py
new file mode 100644
index 00000000..509ea11b
--- /dev/null
+++ b/nextline/utils/timer.py
@@ -0,0 +1,49 @@
+import time
+
+
+class Timer:
+    '''A timer.
+
+    Parameters
+    ----------
+    timeout :
+        The timeout in seconds.
+
+
+    Examples
+    --------
+    >>> timer = Timer(timeout=0.01)
+    >>> timer.elapsed() < 0.01
+    True
+
+    >>> timer.is_timeout()
+    False
+
+    >>> timer.restart()
+
+    >>> timer.is_timeout()
+    False
+
+    >>> time.sleep(0.01)
+
+    >>> timer.is_timeout()
+    True
+
+
+    '''
+
+    def __init__(self, timeout: float) -> None:
+        self._timeout = timeout
+        self._start = time.perf_counter()
+
+    def restart(self) -> None:
+        '''Restart the timer.'''
+        self._start = time.perf_counter()
+
+    def elapsed(self) -> float:
+        '''Return the time passed in seconds.'''
+        return time.perf_counter() - self._start
+
+    def is_timeout(self) -> bool:
+        '''Return True if the timeout is reached.'''
+        return self.elapsed() > self._timeout