diff --git a/kopf/toolkits/runner.py b/kopf/toolkits/runner.py
index 2ce28b42..06044720 100644
--- a/kopf/toolkits/runner.py
+++ b/kopf/toolkits/runner.py
@@ -67,7 +67,6 @@ def __init__(
         self.kwargs = kwargs
         self.reraise = reraise
         self.timeout = timeout
-        self._loop = asyncio.new_event_loop()
         self._stop = threading.Event()
         self._ready = threading.Event()  # NB: not asyncio.Event!
         self._thread = threading.Thread(target=self._target)
@@ -90,8 +89,6 @@ def __exit__(
         # but instead wait for the thread+loop (CLI command) to finish.
         self._stop.set()
         self._thread.join(timeout=self.timeout)
-        self._loop.run_until_complete(self._loop.shutdown_asyncgens())
-        self._loop.close()
 
         # If the thread is not finished, it is a bigger problem than exceptions.
         if self._thread.is_alive():
@@ -115,7 +112,8 @@ def _target(self) -> None:
 
         # Every thread must have its own loop. The parent thread (pytest)
         # needs to know when the loop is set up, to be able to shut it down.
-        asyncio.set_event_loop(self._loop)
+        loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(loop)
         self._ready.set()
 
         # Execute the requested CLI command in the thread & thread's loop.
@@ -128,6 +126,17 @@ def _target(self) -> None:
             self._future.set_exception(e)
         else:
             self._future.set_result(result)
+        finally:
+
+            # Shut down the API-watching streams.
+            loop.run_until_complete(loop.shutdown_asyncgens())
+
+            # Shut down the transports and prevent ResourceWarning: unclosed transport.
+            # See: https://docs.aiohttp.org/en/stable/client_advanced.html#graceful-shutdown
+            # TODO: Try a hack: https://github.com/aio-libs/aiohttp/issues/1925#issuecomment-575754386
+            loop.run_until_complete(asyncio.sleep(1.0))
+
+            loop.close()
 
     @property
     def future(self) -> ResultFuture: