diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
index 3c45621390be44f..7a5b7f2bb0fdc68 100644
--- a/Lib/test/libregrtest/save_env.py
+++ b/Lib/test/libregrtest/save_env.py
@@ -61,7 +61,7 @@ def __init__(self, testname, verbose=0, quiet=False, *, pgo=False):
                  'os.environ', 'sys.path', 'sys.path_hooks', '__import__',
                  'warnings.filters', 'asyncore.socket_map',
                  'logging._handlers', 'logging._handlerList', 'sys.gettrace',
-                 'sys.warnoptions',
+                 'sys.warnoptions', 'idlerc',
                  # multiprocessing.process._cleanup() may release ref
                  # to a thread, so check processes first.
                  'multiprocessing.process._dangling', 'threading._dangling',
@@ -253,6 +253,29 @@ def get_warnings_showwarning(self):
     def restore_warnings_showwarning(self, fxn):
         warnings.showwarning = fxn
 
+    def get_idlerc(self):
+        import pathlib
+        from idlelib.config import idleConf
+        idlerc_dir = pathlib.Path(idleConf.GetUserCfgDir())
+
+        saved = {}
+        for filename in idlerc_dir.glob('*'):
+            with open(filename) as f:
+                saved[filename] = f.read()
+        return saved
+
+    def restore_idlerc(self, saved):
+        import pathlib
+        from idlelib.config import idleConf
+        idlerc_dir = pathlib.Path(idleConf.GetUserCfgDir())
+
+        for filename in idlerc_dir.glob('*'):
+            support.unlink(filename)
+
+        for filename in saved:
+            with open(filename, 'w') as f:
+                f.write(saved[filename])
+
     def resource_info(self):
         for name in self.resources:
             method_suffix = name.replace('.', '_')
diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index a544f880d2be01b..f5908de00b041b9 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -951,6 +951,30 @@ def test_env_changed(self):
         self.check_executed_tests(output, [testname], env_changed=testname,
                                   fail_env_changed=True)
 
+    def test_env_user_idlerc_changed(self):
+        code = textwrap.dedent("""
+            import unittest
+            from idlelib.config import idleConf
+
+            class Tests(unittest.TestCase):
+                def test_user_idlerc_changed(self):
+                    default = idleConf.GetOption('main', 'Theme', 'default',
+                                                 type='bool')
+                    idleConf.SetOption('main', 'Theme', 'default',
+                                       str(not default))
+                    idleConf.SaveUserCfgFiles()
+        """)
+        testname = self.create_test(code=code)
+
+        # don't fail by default
+        output = self.run_tests(testname)
+        self.check_executed_tests(output, [testname], env_changed=testname)
+
+        # fail with --fail-env-changed
+        output = self.run_tests("--fail-env-changed", testname, exitcode=3)
+        self.check_executed_tests(output, [testname], env_changed=testname,
+                                  fail_env_changed=True)
+
 
 if __name__ == '__main__':
     unittest.main()