diff --git a/tools/check_api_compatible.py b/tools/check_api_compatible.py
index cc307a884663303aae7978f5c157cca5571c5b8d..f91112abd6460f06750a054eadf6aaf4e172026d 100644
--- a/tools/check_api_compatible.py
+++ b/tools/check_api_compatible.py
@@ -75,7 +75,7 @@ def check_compatible(old_api_spec, new_api_spec):
 
 def check_compatible_str(old_api_spec_str, new_api_spec_str):
     patArgSpec = re.compile(
-        r'args=(.*), varargs=.*defaults=\((.*)\), kwonlyargs=.*')
+        r'args=(.*), varargs=.*defaults=(None|\((.*)\)), kwonlyargs=.*')
     mo_o = patArgSpec.search(old_api_spec_str)
     mo_n = patArgSpec.search(new_api_spec_str)
     if not (mo_o and mo_n):
@@ -86,8 +86,10 @@ def check_compatible_str(old_api_spec_str, new_api_spec_str):
 
     args_o = eval(mo_o.group(1))
     args_n = eval(mo_n.group(1))
-    defaults_o = mo_o.group(2).split(', ')
-    defaults_n = mo_n.group(2).split(', ')
+    defaults_o = mo_o.group(2) if mo_o.group(3) is None else mo_o.group(3)
+    defaults_n = mo_n.group(2) if mo_n.group(3) is None else mo_n.group(3)
+    defaults_o = defaults_o.split(', ') if defaults_o else []
+    defaults_n = defaults_n.split(', ') if defaults_n else []
     return _check_compatible(args_o, args_n, defaults_o, defaults_n)
 
 
diff --git a/tools/test_check_api_compatible.py b/tools/test_check_api_compatible.py
index 23debef657fa18ffd717913efe43e60d7c5a29e1..24e7b3a8f8acb1acbf47f6375d5ffc26e9b74b30 100644
--- a/tools/test_check_api_compatible.py
+++ b/tools/test_check_api_compatible.py
@@ -105,6 +105,11 @@ class Test_check_compatible_str(unittest.TestCase):
         argspec_o = self.argspec_str_o
         self.assertFalse(check_compatible_str(argspec_o, argspec_n))
 
+    def test_args_defaults_None(self):
+        argspec_o = """inspect.FullArgSpec(args=['filename'], varargs=None, varkw=None, defaults=None, kwonlyargs=[], kwonlydefaults=None, annotations={'filename': <class 'str'>})"""
+        argspec_n = """inspect.FullArgSpec(args=['filename'], varargs=None, varkw=None, defaults=None, kwonlyargs=[], kwonlydefaults=None, annotations={'filename': <class 'str'>})"""
+        self.assertTrue(check_compatible_str(argspec_o, argspec_n))
+
 
 class Test_read_argspec_from_file(unittest.TestCase):
     def setUp(self) -> None: