diff --git a/pyproject.toml b/pyproject.toml
index 6dd85b8..fbbdc9c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "i21y"
-version = "0.1.0.post1"
+version = "0.1.1"
 description = "The library for i18n support."
 authors = ["Takagi Tasuku <tasuren@outlook.jp>"]
 license = "MIT"
diff --git a/src/i21y/__init__.py b/src/i21y/__init__.py
index 1c1cc07..9f58bd9 100644
--- a/src/i21y/__init__.py
+++ b/src/i21y/__init__.py
@@ -1,7 +1,7 @@
 "tasuren - i21y"
 
 __author__ = "Takagi Tasuku"
-__version__ = "0.1.0.post1"
+__version__ = "0.1.1"
 __all__ = ("Translator", "I21YError", "TranslationNotFound", "locale_str")
 
 from .translator import Translator
diff --git a/src/i21y/utils.py b/src/i21y/utils.py
index 6a740e1..7983804 100644
--- a/src/i21y/utils.py
+++ b/src/i21y/utils.py
@@ -66,24 +66,26 @@ def join_raw(self, *other: str | locale_str) -> str:
     @overload
     def join(
         self: ..., *other: str | locale_str,
-        cls: type[AdtnlClsT] = None
+        cls: type[AdtnlClsT] = None, **extras: Any
     ) -> AdtnlClsT: ...
     @overload
     def join(
         self: SelfT, *other: str | locale_str,
-        cls: None = None
+        cls: None = None, **extras: Any
     ) -> SelfT: ...
     def join(
         self: SelfT, *other: str | locale_str,
-        cls: type[AdtnlClsT] | None = None
+        cls: type[AdtnlClsT] | None = None, **extras: Any
     ) -> SelfT | AdtnlClsT:
         """A version of :meth:`locale_str.join_raw` that returns the instance of the class that self.
 
         Args:
-            *other: Target strings."""
+            *other: Target strings.
+            cls: The :class:`.locale_str` used to create the instance.
+            **extras: The value to pass to the ``extras`` argument of the constructor of :class:`.locale_str`."""
         cls = cls or self.__class__ # type: ignore
         assert cls is not None
-        return cls(self.join_raw(*other))
+        return cls(self.join_raw(*other), **extras)
 
     def __truediv__(self: SelfT, other: LocaleStr | Iterable[LocaleStr]) -> SelfT:
         if isinstance(other, str | locale_str):
diff --git a/tests/test_locale_str.py b/tests/test_locale_str.py
index 66d430a..bf72ade 100644
--- a/tests/test_locale_str.py
+++ b/tests/test_locale_str.py
@@ -11,4 +11,6 @@
 assert str(LEFT) == str(RIGHT)
 assert LEFT.test == RIGHT.test
 
-assert BASE // "kakikukeko" == "aiueo.kakikukeko"
\ No newline at end of file
+assert BASE // "kakikukeko" == "aiueo.kakikukeko"
+
+assert BASE.join("test", a="b").extras["a"] == "b"
\ No newline at end of file