diff --git a/pdm_build.py b/pdm_build.py
index 32ad434..063fcad 100644
--- a/pdm_build.py
+++ b/pdm_build.py
@@ -29,8 +29,9 @@ def pdm_build_initialize(context: Context) -> None:
 
 def pdm_build_update_files(context: Context, files: dict[str, Path]) -> None:
     from pyfuture.hooks import pdm as pyfuture_pdm_hooks
+    from pyfuture.utils import get_target
 
     hook_config = pyfuture_pdm_hooks.get_hook_config(context)
     target_str = pyfuture_pdm_hooks.get_target_str(hook_config)
-    target = pyfuture_pdm_hooks.get_target(target_str)
+    target = get_target(target_str)
     pyfuture_pdm_hooks.pdm_build_update_files(context, files, target)
diff --git a/pyfuture/__main__.py b/pyfuture/__main__.py
index 4ee6288..783fb6b 100644
--- a/pyfuture/__main__.py
+++ b/pyfuture/__main__.py
@@ -9,7 +9,7 @@
 from rich.logging import RichHandler
 from rich.style import Style
 
-from pyfuture.utils import transfer_file
+from pyfuture.utils import get_target, transfer_file
 
 app = typer.Typer()
 
@@ -21,21 +21,21 @@ def init_logger(log_level: str):
 
 
 @app.command()
-def transfer(src_file: Path, tgt_file: Path, *, target: str = "3.9", log_level: str = "INFO"):
+def transfer(src_file: Path, tgt_file: Path, *, target: str = "py39", log_level: str = "INFO"):
     """
     Transfer code from src_file and write to tgt_file.
     """
-    assert target == "3.9", "PyFuture is very early stage, not support target argument yet"
+
     init_logger(log_level)
     transfer_file(src_file, tgt_file)
 
 
 @app.command()
-def watch(src_file: Path, tgt_file: Path, *, target: str = "3.9", log_level: str = "INFO"):  # pragma: no cover
+def watch(src_file: Path, tgt_file: Path, *, target: str = "py39", log_level: str = "INFO"):  # pragma: no cover
     """
     Transfer all python files in src_dir to build_dir, and watch for changes.
     """
-    assert target == "3.9", "PyFuture is very early stage, not support target argument yet"
+
     init_logger(log_level)
     transfer_file(src_file, tgt_file)
 
@@ -46,18 +46,18 @@ def watch(src_file: Path, tgt_file: Path, *, target: str = "3.9", log_level: str
             match mode:
                 case Change.modified:
                     logger.info("Source file has been modified")
-                    transfer_file(Path(path), tgt_file)
+                    transfer_file(Path(path), tgt_file, target=get_target(target))
                 case Change.deleted:
                     logger.info("Source file has been deleted")
                     break
 
 
 @app.command()
-def transfer_dir(src_dir: Path, build_dir: Path, *, target: str = "3.9", log_level: str = "INFO"):
+def transfer_dir(src_dir: Path, build_dir: Path, *, target: str = "py39", log_level: str = "INFO"):
     """
     Transfer all python files in src_dir to build_dir.
     """
-    assert target == "3.9", "PyFuture is very early stage, not support target argument yet"
+
     init_logger(log_level)
 
     for src_file in src_dir.glob("**/*.py"):
@@ -66,11 +66,11 @@ def transfer_dir(src_dir: Path, build_dir: Path, *, target: str = "3.9", log_lev
 
 
 @app.command()
-def watch_dir(src_dir: Path, build_dir: Path, *, target: str = "3.9", log_level: str = "INFO"):  # pragma: no cover
+def watch_dir(src_dir: Path, build_dir: Path, *, target: str = "py39", log_level: str = "INFO"):  # pragma: no cover
     """
     Transfer all python files in src_dir to build_dir, and watch for changes.
     """
-    assert target == "3.9", "PyFuture is very early stage, not support target argument yet"
+
     init_logger(log_level)
     transfer_dir(src_dir, build_dir, target=target)
 
diff --git a/pyfuture/hooks/pdm.py b/pyfuture/hooks/pdm.py
index 518cb77..1d976b9 100644
--- a/pyfuture/hooks/pdm.py
+++ b/pyfuture/hooks/pdm.py
@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 import os
-import sys
 from pathlib import Path
 
 from pdm.backend.hooks.base import Context
@@ -26,28 +25,10 @@ def get_target_str(hook_config: dict) -> str | None:
     """
     target_str = os.environ.get("PYFUTURE_TARGET", None)
     if target_str is None:
-        target_str = hook_config.get("target", None)
+        target_str = hook_config.get("target")
     return target_str
 
 
-def get_target(target_str: str | None) -> tuple[int, int]:
-    """
-    Get target version from target string.
-
-    Example:
-    >>> get_target(None) == sys.version_info[:2]
-    True
-    >>> get_target("py39")
-    (3, 9)
-    >>> get_target("py310")
-    (3, 10)
-    """
-    if target_str is None:
-        return sys.version_info[:2]
-    else:
-        return (int(target_str[2:3]), int(target_str[3:]))
-
-
 def get_hook_config(context: Context) -> dict:  # pragma: no cover
     return context.config.data.get("tool", {}).get("pdm", {}).get("build", {}).get("hooks", {}).get("pyfuture", {})
 
diff --git a/pyfuture/utils.py b/pyfuture/utils.py
index 7eb921c..8cd0c88 100644
--- a/pyfuture/utils.py
+++ b/pyfuture/utils.py
@@ -2,6 +2,7 @@
 
 import contextlib
 import io
+import sys
 from pathlib import Path
 
 import libcst as cst
@@ -10,6 +11,24 @@
 from .codemod.utils import RuleSet, get_transformers
 
 
+def get_target(target_str: str | None) -> tuple[int, int]:
+    """
+    Get target version from target string.
+
+    Example:
+    >>> get_target(None) == sys.version_info[:2]
+    True
+    >>> get_target("py39")
+    (3, 9)
+    >>> get_target("py310")
+    (3, 10)
+    """
+    if target_str is None:
+        return sys.version_info[:2]
+    else:
+        return (int(target_str[2:3]), int(target_str[3:]))
+
+
 def apply_transformer(
     transformers: list[type[Codemod]],
     code: str,