diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index de8d65a..ef6e94b 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -6,10 +6,12 @@
 import random
 import subprocess
 import sys
+import textwrap
 import time
 import unittest
 from test import support
 from test.support import MISSING_C_DOCSTRINGS
+from test.script_helper import assert_python_failure
 try:
     import _posixsubprocess
 except ImportError:
@@ -21,6 +23,9 @@
 # Skip this test if the _testcapi module isn't available.
 _testcapi = support.import_module('_testcapi')
 
+# Were we compiled --with-pydebug or with #define Py_DEBUG?
+Py_DEBUG = hasattr(sys, 'gettotalrefcount')
+
 
 def testfunction(self):
     """some doc"""
@@ -167,6 +172,45 @@
         o @= m1
         self.assertEqual(o, ("matmul", 42, m1))
 
+    def test_return_null_without_error(self):
+        # Issue #23571: A function must not return NULL without setting an
+        # error
+        if Py_DEBUG:
+            code = textwrap.dedent("""
+                import _testcapi
+                from test import support
+
+                with support.SuppressCrashReport():
+                    _testcapi.return_null_without_error()
+            """)
+            rc, out, err = assert_python_failure('-c', code)
+            self.assertIn(b'_Py_CheckFunctionResult: Assertion', err)
+        else:
+            with self.assertRaises(SystemError) as cm:
+                _testcapi.return_null_without_error()
+            self.assertRegex(str(cm.exception),
+                             'return_null_without_error.* '
+                             'returned NULL without setting an error')
+
+    def test_return_result_with_error(self):
+        # Issue #23571: A function must not return a result with an error set
+        if Py_DEBUG:
+            code = textwrap.dedent("""
+                import _testcapi
+                from test import support
+
+                with support.SuppressCrashReport():
+                    _testcapi.return_result_with_error()
+            """)
+            rc, out, err = assert_python_failure('-c', code)
+            self.assertIn(b'_Py_CheckFunctionResult: Assertion', err)
+        else:
+            with self.assertRaises(SystemError) as cm:
+                _testcapi.return_result_with_error()
+            self.assertRegex(str(cm.exception),
+                             'return_result_with_error.* '
+                             'returned a result with an error set')
+
 
 @unittest.skipUnless(threading, 'Threading required for this test.')
 class TestPendingCalls(unittest.TestCase):