diff --git a/ruff.toml b/ruff.toml
index d55fd9f7..5a23da74 100644
--- a/ruff.toml
+++ b/ruff.toml
@@ -14,6 +14,7 @@ lint.ignore = [
     "E501",  # line-too-long
     "E741",  # ambiguous-variable-name
     "E402",  # module-import-not-at-top-of-file
+    "FURB189",  # subclassing str
     "S101",  # use of assert
     "PERF203", # try-except within loop
     "PLC0415",  # import-outside-top-level
diff --git a/tatsu/ast.py b/tatsu/ast.py
index bfba54c0..95db84a1 100644
--- a/tatsu/ast.py
+++ b/tatsu/ast.py
@@ -7,7 +7,7 @@
 from .util import asjson, is_list
 
 
-class AST(dict):  # noqa: FURB189
+class AST(dict):
     _frozen = False
 
     def __init__(self, *args, **kwargs):
diff --git a/tatsu/buffering.py b/tatsu/buffering.py
index 87358d99..bf3a58a7 100644
--- a/tatsu/buffering.py
+++ b/tatsu/buffering.py
@@ -23,7 +23,6 @@
 )
 from .tokenizing import Tokenizer
 from .util import (
-    RETYPE,
     contains_sublist,
     extend_list,
     identity,
@@ -85,7 +84,7 @@ def build_whitespace_re(whitespace):
             return DEFAULT_WHITESPACE_RE
         if whitespace in {None, ''}:
             return None
-        elif isinstance(whitespace, RETYPE):
+        elif isinstance(whitespace, re.Pattern):
             return whitespace
         elif whitespace:
             if not isinstance(whitespace, str):
@@ -354,7 +353,7 @@ def matchre(self, pattern):
         return token
 
     def _scanre(self, pattern):
-        if isinstance(pattern, RETYPE):
+        if isinstance(pattern, re.Pattern):
             cre = pattern
         else:
             cre = re.compile(pattern, re.MULTILINE)
diff --git a/tatsu/codegen/objectmodel.py b/tatsu/codegen/objectmodel.py
index d52ea9df..bc787f59 100644
--- a/tatsu/codegen/objectmodel.py
+++ b/tatsu/codegen/objectmodel.py
@@ -67,11 +67,11 @@ def _get_full_name(cls):
     # Try to reference the class
     try:
         idents = name.split('.')
-        _cls = getattr(module, idents[0])
+        cls_ = getattr(module, idents[0])
         for ident in idents[1:]:
-            _cls = getattr(_cls, ident)
+            cls_ = getattr(cls_, ident)
 
-        assert _cls == cls
+        assert cls_ == cls
     except AttributeError as e:
         raise CodegenError(
             "Couldn't find base type, it has to be importable",
diff --git a/tatsu/codegen/python.py b/tatsu/codegen/python.py
index 31e0dea9..d1d2fdcd 100755
--- a/tatsu/codegen/python.py
+++ b/tatsu/codegen/python.py
@@ -3,13 +3,14 @@
 """
 from __future__ import annotations
 
+import re
 import textwrap
 
 from .. import grammars
 from ..collections import OrderedSet as oset
 from ..exceptions import CodegenError
 from ..objectmodel import BASE_CLASS_TOKEN, Node
-from ..util import RETYPE, compress_seq, indent, safe_name, timestamp, trim
+from ..util import compress_seq, indent, safe_name, timestamp, trim
 from .cgbase import CodeGenerator, ModelRenderer
 
 
@@ -448,7 +449,7 @@ def render_fields(self, fields):
         whitespace = self.node.config.whitespace
         if not whitespace:
             whitespace = 'None'
-        elif isinstance(whitespace, RETYPE):
+        elif isinstance(whitespace, re.Pattern):
             whitespace = repr(whitespace)
         else:
             whitespace = f're.compile(r"{whitespace}")'
diff --git a/tatsu/contexts.py b/tatsu/contexts.py
index 12873fdb..50d7df30 100644
--- a/tatsu/contexts.py
+++ b/tatsu/contexts.py
@@ -101,7 +101,7 @@ def isname(impl):
     return impl
 
 
-class closure(list):  # noqa: FURB189
+class closure(list):
     def __hash__(self):
         return hash(tuple(self))
 
diff --git a/tatsu/g2e/semantics.py b/tatsu/g2e/semantics.py
index 982ed777..ccf0b497 100644
--- a/tatsu/g2e/semantics.py
+++ b/tatsu/g2e/semantics.py
@@ -9,7 +9,7 @@
 
 def camel2py(name):
     return re.sub(
-        '([a-z0-9])([A-Z])',
+        r'([a-z0-9])([A-Z])',
         lambda m: m.group(1) + '_' + m.group(2).lower(),
         name,
     )
diff --git a/tatsu/grammars.py b/tatsu/grammars.py
index 65def8b9..4ac6c127 100644
--- a/tatsu/grammars.py
+++ b/tatsu/grammars.py
@@ -22,7 +22,7 @@
 PRAGMA_RE = r'^\s*#include.*$'
 
 
-class _ref(str):  # noqa: FURB189
+class _ref(str):
     def __repr__(self):
         return f'<{self}>'
 
@@ -519,7 +519,7 @@ def _to_str(self, lean=False):
 
         if multi:
             return '\n|\n'.join(indent(o) for o in options)
-        elif len(options) and len(single) > PEP8_LLEN:
+        elif options and len(single) > PEP8_LLEN:
             return '| ' + '\n| '.join(o for o in options)
         else:
             return single
diff --git a/tatsu/infos.py b/tatsu/infos.py
index 6ec898ad..0efb982f 100644
--- a/tatsu/infos.py
+++ b/tatsu/infos.py
@@ -12,7 +12,7 @@
 from .util.unicode_characters import C_DERIVE
 
 
-class UndefinedStr(str):  # noqa: FURB189
+class UndefinedStr(str):
     pass
 
 
diff --git a/tatsu/util/_common.py b/tatsu/util/_common.py
index c0819064..48c15038 100644
--- a/tatsu/util/_common.py
+++ b/tatsu/util/_common.py
@@ -27,9 +27,6 @@
 logger.addHandler(ch)
 
 
-RETYPE = type(re.compile('.'))
-
-
 ESCAPE_SEQUENCE_RE = re.compile(
     r"""
     ( \\U........      # 8-digit Unicode escapes
diff --git a/tatsu/util/misc.py b/tatsu/util/misc.py
index 89688550..1abf21c1 100644
--- a/tatsu/util/misc.py
+++ b/tatsu/util/misc.py
@@ -4,8 +4,6 @@
 from collections.abc import Iterable
 from typing import TypeVar
 
-from ._common import RETYPE
-
 _T = TypeVar('_T')
 
 _undefined = object()  # unique object for when None is not a good default
@@ -62,7 +60,7 @@ def findalliter(pattern, string, pos=None, endpos=None, flags=0):
     """
     r = (
         pattern
-        if isinstance(pattern, RETYPE)
+        if isinstance(pattern, re.Pattern)
         else re.compile(pattern, flags=flags)
     )
     if endpos is not None:
diff --git a/tatsu/walkers.py b/tatsu/walkers.py
index 3de070ea..7762a4d7 100644
--- a/tatsu/walkers.py
+++ b/tatsu/walkers.py
@@ -74,7 +74,7 @@ def pythonize_match(m):
 
             # walk__pythonic_name with double underscore after walk
             pythonic_name = re.sub(
-                '[A-Z]+', pythonize_match, node_cls.__name__,
+                r'[A-Z]+', pythonize_match, node_cls.__name__,
             )
             if pythonic_name != cammelcase_name:
                 walker = getattr(cls, prefix + pythonic_name, None)
diff --git a/test/parser_equivalence_test.py b/test/parser_equivalence_test.py
index 02b4367f..12b1f599 100644
--- a/test/parser_equivalence_test.py
+++ b/test/parser_equivalence_test.py
@@ -171,8 +171,9 @@ def test_none_whitespace():
     output = parser.parse(input, parseinfo=False)
     assert output == ('This is a', ' test')
 
+
 def test_sep_join():
-    grammar = """
+    grammar = r"""
     @@grammar::numbers
 
     start
@@ -186,6 +187,4 @@ def test_sep_join():
     digit = /\d+/ ;
     """
     parser = generate_and_load_parser('W', grammar)
-    ast = parser.parse('1,2,3,4', nameguard=False)
-
-
+    parser.parse('1,2,3,4', nameguard=False)
diff --git a/test/zzz_bootstrap/bootstrap_test.py b/test/zzz_bootstrap/bootstrap_test.py
index 1fde06e3..309ebc54 100644
--- a/test/zzz_bootstrap/bootstrap_test.py
+++ b/test/zzz_bootstrap/bootstrap_test.py
@@ -9,7 +9,6 @@
 import unittest
 from pathlib import Path
 
-from tatsu import util
 from tatsu.ngcodegen import codegen
 from tatsu.parser import EBNFParser, GrammarGenerator
 from tatsu.parser_semantics import EBNFGrammarSemantics
@@ -163,8 +162,7 @@ def walk_default(self, o, children):
         except ImportError:
             print('PyGraphViz not found!')
         else:
-            if not util.PY37:
-                draw('./tmp/13.png', g11)
+            draw('./tmp/13.png', g11)
 
 
 def suite():