diff --git a/stdlib/base64.pyi b/stdlib/base64.pyi
index 24830cbfb..4629c95d0 100644
--- a/stdlib/base64.pyi
+++ b/stdlib/base64.pyi
@@ -27,13 +27,13 @@ if sys.version_info >= (3, 10):
     __all__ += ["b32hexencode", "b32hexdecode"]
 
 def b64encode(s: ReadableBuffer, altchars: ReadableBuffer | None = None) -> bytes: ...
-def b64decode(s: str | ReadableBuffer, altchars: ReadableBuffer | None = None, validate: bool = False) -> bytes: ...
+def b64decode(s: str | ReadableBuffer, altchars: str | ReadableBuffer | None = None, validate: bool = False) -> bytes: ...
 def standard_b64encode(s: ReadableBuffer) -> bytes: ...
 def standard_b64decode(s: str | ReadableBuffer) -> bytes: ...
 def urlsafe_b64encode(s: ReadableBuffer) -> bytes: ...
 def urlsafe_b64decode(s: str | ReadableBuffer) -> bytes: ...
 def b32encode(s: ReadableBuffer) -> bytes: ...
-def b32decode(s: str | ReadableBuffer, casefold: bool = False, map01: bytes | None = None) -> bytes: ...
+def b32decode(s: str | ReadableBuffer, casefold: bool = False, map01: str | ReadableBuffer | None = None) -> bytes: ...
 def b16encode(s: ReadableBuffer) -> bytes: ...
 def b16decode(s: str | ReadableBuffer, casefold: bool = False) -> bytes: ...