Feb 3, 2026 · Feb 3, 2026 · Feb 3, 2026 · Feb 3, 2026 · Feb 3, 2026 · Feb 3, 2026
diff --git a/Lib/pickle.py b/Lib/pickle.py
 stack=self.stack
 args=stack.pop()
 func=stack[-1]
 ifnotisinstance(args,tuple):
 raiseTypeError("argument list must be a tuple")
 stack[-1]=func(*args)
 dispatch[REDUCE[0]]=load_reduce

diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
 self.assertEqual(self.loads(b'cbuiltins\nint\n)R.'),0)
 self.check_unpickling_error(TypeError,b'N)R.')
 self.check_unpickling_error(TypeError,b'cbuiltins\nint\nNR.')
 self.check_unpickling_error(TypeError,b'cbuiltins\nint\nNR.')

 deftest_bad_newobj(self):
 error= (pickle.UnpicklingError,TypeError)
diff --git a/Misc/NEWS.d/next/Library/2026-02-03-12-00-00.gh-issue-144412.q7KpXg.rst b/Misc/NEWS.d/next/Library/2026-02-03-12-00-00.gh-issue-144412.q7KpXg.rst
 ``pickle.load_reduce()`` now requires a tuple for ``REDUCE`` arguments to
 match ``_pickle``; non-tuple argument lists now raise ``TypeError``.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1724,6 +1724,8 @@ def load_reduce(self):
		stack=self.stack
		args=stack.pop()
		func=stack[-1]
		ifnotisinstance(args,tuple):
		raiseTypeError("argument list must be a tuple")
		stack[-1]=func(*args)
		dispatch[REDUCE[0]]=load_reduce

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1435,6 +1435,7 @@ def test_bad_reduce(self):
		self.assertEqual(self.loads(b'cbuiltins\nint\n)R.'),0)
		self.check_unpickling_error(TypeError,b'N)R.')
		self.check_unpickling_error(TypeError,b'cbuiltins\nint\nNR.')
		self.check_unpickling_error(TypeError,b'cbuiltins\nint\nNR.')

		deftest_bad_newobj(self):
		error= (pickle.UnpicklingError,TypeError)
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		``pickle.load_reduce()`` now requires a tuple for ``REDUCE`` arguments to
		match ``_pickle``; non-tuple argument lists now raise ``TypeError``.