diff --git a/stubs/reportlab/reportlab/lib/utils.pyi b/stubs/reportlab/reportlab/lib/utils.pyi
index d69f6a7c243b..578ab1fc0e98 100644
--- a/stubs/reportlab/reportlab/lib/utils.pyi
+++ b/stubs/reportlab/reportlab/lib/utils.pyi
@@ -1,11 +1,13 @@
 import datetime
 import zipimport
 from _typeshed import Incomplete, SupportsItems
+from builtins import _ClassInfo
 from collections.abc import Generator, Iterable, MutableMapping
 from os import PathLike
 from time import _TimeTuple, struct_time
 from types import TracebackType
 from typing import AnyStr, Final, Literal, TypeVar, overload, type_check_only
+from typing_extensions import TypeIs
 from urllib.request import _UrlopenRet
 
 from reportlab.lib.rltempfile import get_rl_tempdir as get_rl_tempdir, get_rl_tempfile as get_rl_tempfile
@@ -31,10 +33,10 @@ __UNSET__: Final[_UNSET_]
 isPyPy: bool
 
 def isFunction(v: object) -> bool: ...
-def isMethod(v: object, mt=...) -> bool: ...
+def isMethod(v: object, mt: type = ...) -> bool: ...
 def isModule(v: object) -> bool: ...
-def isSeq(v: object, _st=...) -> bool: ...
-def isNative(v: object) -> bool: ...
+def isSeq(v: object, _st: _ClassInfo = ...) -> bool: ...
+def isNative(v: object) -> TypeIs[str]: ...
 
 strTypes: tuple[type[str], type[bytes]]
 
@@ -43,10 +45,10 @@ def asUnicode(v: str | bytes, enc: str = "utf8") -> str: ...
 def asUnicodeEx(v: str | bytes, enc: str = "utf8") -> str: ...
 def asNative(v: str | bytes, enc: str = "utf8") -> str: ...
 def int2Byte(i: int) -> bytes: ...
-def isStr(v: object) -> bool: ...
-def isBytes(v: object) -> bool: ...
-def isUnicode(v: object) -> bool: ...
-def isClass(v: object) -> bool: ...
+def isStr(v: object) -> TypeIs[str | bytes]: ...
+def isBytes(v: object) -> TypeIs[bytes]: ...
+def isUnicode(v: object) -> TypeIs[str]: ...
+def isClass(v: object) -> TypeIs[type]: ...
 def isNonPrimitiveInstance(x: object) -> bool: ...
 def instantiated(v: object) -> bool: ...
 def bytestr(x: object, enc: str = "utf8") -> bytes: ...