diff --git a/asyncer/_compat.py b/asyncer/_compat.py
index ade175e..687e962 100644
--- a/asyncer/_compat.py
+++ b/asyncer/_compat.py
@@ -1,12 +1,17 @@
 # AnyIO 4.1.0 renamed cancellable to abandon_on_cancel
 import importlib
 import importlib.metadata
+import sys
 from typing import Callable, TypeVar, Union
 
 import anyio
 import anyio.to_thread
 from anyio import CapacityLimiter
-from typing_extensions import TypeVarTuple, Unpack
+
+if sys.version_info >= (3, 11):
+    from typing import TypeVarTuple, Unpack
+else:
+    from typing_extensions import TypeVarTuple, Unpack
 
 ANYIO_VERSION = importlib.metadata.version("anyio")
 
diff --git a/asyncer/_main.py b/asyncer/_main.py
index 78117e4..19d8318 100644
--- a/asyncer/_main.py
+++ b/asyncer/_main.py
@@ -135,7 +135,7 @@ async def do_work(name: str) -> str:
         async with asyncer.create_task_group() as task_group:
             result1 = task_group.soonify(do_work)(name="task 1")
             result2 = task_group.soonify(do_work)(name="task 2")
-            await anyio.sleep(0)
+            await anyio.lowlevel.checkpoint()
             if not result1.pending:
                 print(result1.value)
             if not result2.pending:
diff --git a/poetry.toml b/poetry.toml
deleted file mode 100644
index 084377a..0000000
--- a/poetry.toml
+++ /dev/null
@@ -1,2 +0,0 @@
-[virtualenvs]
-create = false
diff --git a/pyproject.toml b/pyproject.toml
index 3497d51..82f6d79 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,7 +32,7 @@ classifiers = [
 ]
 dependencies = [
     "anyio >=3.4.0,<5.0",
-    "typing_extensions >=4.8.0; python_version < '3.10'"
+    "typing_extensions >=4.8.0; python_version < '3.11'"
 ]
 
 [project.urls]