diff --git a/etg/_core.py b/etg/_core.py
index 67acbdc78a..3addfb5f75 100644
--- a/etg/_core.py
+++ b/etg/_core.py
@@ -291,11 +291,16 @@ def run():
             """)
 
 
+    module.addPyCode('import typing', order=10)
     module.addPyCode("""\
-            _T = TypeVar('_T')
-            _P = ParamSpec('_P')
-    """)
-    module.addPyFunction('CallAfter', '(callableObj: Callable[_P, _T], *args: _P.args, **kw: _P.kwargs) -> None', doc="""\
+        _T = typing.TypeVar('_T')
+        try:
+            _P = typing.ParamSpec('_P')
+        except AttributeError:
+            import typing_extensions
+            _P = typing_extensions.ParamSpec('_P')
+        """)
+    module.addPyFunction('CallAfter', '(callableObj: typing.Callable[_P, _T], *args: _P.args, **kw: _P.kwargs) -> None', doc="""\
             Call the specified function after the current and pending event
             handlers have been completed.  This is also good for making GUI
             method calls from non-GUI threads.  Any extra positional or
@@ -326,7 +331,7 @@ def run():
             wx.PostEvent(app, evt)""")
 
 
-    module.addPyClass('CallLater', ['Generic[_P, _T]'],
+    module.addPyClass('CallLater', ['typing.Generic[_P, _T]'],
         doc="""\
             A convenience class for :class:`wx.Timer`, that calls the given callable
             object once after the given amount of milliseconds, passing any
@@ -346,7 +351,7 @@ def run():
             """,
         items = [
             PyCodeDef('__instances = {}'),
-            PyFunctionDef('__init__', '(self, millis, callableObj: Callable[_P, _T], *args: _P.args, **kwargs: _P.kwargs) -> None',
+            PyFunctionDef('__init__', '(self, millis, callableObj: typing.Callable[_P, _T], *args: _P.args, **kwargs: _P.kwargs) -> None',
                 doc="""\
                     Constructs a new :class:`wx.CallLater` object.
 
@@ -370,7 +375,7 @@ def run():
 
             PyFunctionDef('__del__', '(self)', 'self.Stop()'),
 
-            PyFunctionDef('Start', '(self, millis: int | None=None, *args: _P.args, **kwargs: _P.kwargs) -> None',
+            PyFunctionDef('Start', '(self, millis: typing.Optional[int]=None, *args: _P.args, **kwargs: _P.kwargs) -> None',
                 doc="""\
                     (Re)start the timer
 
diff --git a/etgtools/pi_generator.py b/etgtools/pi_generator.py
index 85ca6929f7..8c1bd157e0 100644
--- a/etgtools/pi_generator.py
+++ b/etgtools/pi_generator.py
@@ -81,7 +81,7 @@
 typing_imports = """\
 from __future__ import annotations
 from enum import IntEnum, IntFlag, auto
-from typing import (Any, overload, TypeAlias, TypeVar, ParamSpec, Generic,
+from typing import (Any, overload, TypeAlias, Generic,
     Union, Optional, List, Tuple, Callable
 )
 try: