diff --git a/arger/parser/classes.py b/arger/parser/classes.py
index 9ca3a64..5b005e1 100644
--- a/arger/parser/classes.py
+++ b/arger/parser/classes.py
@@ -1,7 +1,9 @@
 import argparse
 from enum import Enum
 from inspect import isclass
-from typing import Any, List, Optional, Tuple
+from typing import Any, List, Tuple
+
+from arger.parser.utils import generate_flags
 
 from ..types import UNDEFINED
 from ..typing_utils import match_types
@@ -21,14 +23,7 @@ def get_action(
 
 class Option:
     def __init__(
-        self,
-        flags: Tuple[str, ...] = (),
-        type_: Any = UNDEFINED,
-        default: Any = UNDEFINED,
-        help_: str = "",
-        metavar: Optional[str] = None,
-        required=False,
-        **kwargs,
+        self, flags: List[str], default: Any = UNDEFINED, **kwargs,
     ):
         """Represent optional arguments to the command.
 
@@ -69,6 +64,7 @@ def __init__(
 
         self.flags = flags
 
+        type_ = kwargs.pop('type', UNDEFINED)
         if default is not UNDEFINED:
             kwargs["default"] = default
 
@@ -82,20 +78,20 @@ def __init__(
         elif (type_ is not UNDEFINED) and type_ != bool:
             kwargs.setdefault("type", type_)
 
-        kwargs.setdefault('help', help_)
-        kwargs.setdefault('metavar', metavar)
-        kwargs.setdefault('required', required)
         self.kwargs = kwargs
 
     def add(self, parser: argparse.ArgumentParser):
         return parser.add_argument(*self.flags, **self.kwargs)
 
+    def __repr__(self):
+        return f'{self.__class__.__name__}: {self.flags}, {repr(self.kwargs)}'
+
+    def set_flags(self, option_generator):
+        hlp = self.kwargs.pop('help').split()
+        # generate flags
+        self.flags = generate_flags(self.flags[0], hlp, option_generator)
+        self.kwargs['help'] = " ".join(hlp)
+
 
 class Argument(Option):
     """Represent positional argument that are required."""
-
-    def __init__(
-        self, **kwargs,
-    ):
-        """See Option.__init__'s doc for more info."""
-        super().__init__(required=True, **kwargs)
diff --git a/arger/parser/parser.py b/arger/parser/parser.py
index b1faf65..db82436 100644
--- a/arger/parser/parser.py
+++ b/arger/parser/parser.py
@@ -6,7 +6,7 @@
 
 from ..types import UNDEFINED
 from .classes import Argument, Option
-from .utils import generate_flags, generate_options
+from .utils import generate_options
 
 
 def prepare_arguments(func, param_docs,) -> Dict[str, Option]:
@@ -42,26 +42,26 @@ def prepare_arguments(func, param_docs,) -> Dict[str, Option]:
     option_generator = generate_options()
     next(option_generator)
 
-    arguments: Dict[str, Option] = OrderedDict()
-    for param in positional_params:
-        arguments[param] = Argument(
-            help_=param_docs.get(param, ""),
+    def get_args(param):
+        return dict(
             flags=[param],
-            dest=param,
-            type_=annotations.get(param, UNDEFINED),
+            help=param_docs.get(param, ""),
+            type=annotations.get(param, UNDEFINED),
         )
 
+    arguments: Dict[str, Option] = OrderedDict()
+    for param in positional_params:
+        arguments[param] = Argument(**get_args(param))
+
     for param, default in kw_params.items():
-        hlp = param_docs.get(param, "")
-        flags = generate_flags(param, hlp, option_generator)
-        hlp = " ".join(hlp)
-        arguments[param] = Option(
-            help_=hlp,
-            flags=flags,
-            dest=param,
-            type_=annotations.get(param, UNDEFINED),
-            default=default,
-        )
+        if isinstance(default, Argument):
+            default.flags = [param]
+        elif isinstance(default, Option):
+            default.set_flags(option_generator)
+        else:
+            default = Option(dest=param, default=default, **get_args(param))
+            default.set_flags(option_generator)
+        arguments[param] = default
     return arguments
 
 
diff --git a/arger/parser/utils.py b/arger/parser/utils.py
index 1efbcc2..fb91c9a 100644
--- a/arger/parser/utils.py
+++ b/arger/parser/utils.py
@@ -1,4 +1,4 @@
-from typing import Set
+from typing import List, Set
 
 
 def generate_options():
@@ -25,7 +25,7 @@ def generate_options():
 
 
 def generate_flags(
-    param, param_doc, option_generator,
+    param: str, param_doc: List[str], option_generator,
 ):
     names = []
 
diff --git a/tests/test_fn_parser.py b/tests/test_fn_parser.py
index ef84464..e0e7948 100644
--- a/tests/test_fn_parser.py
+++ b/tests/test_fn_parser.py
@@ -1,4 +1,7 @@
+from collections import OrderedDict
+
 from arger.parser import opterate
+from arger.parser.classes import Argument
 
 from .utils import _reprint
 
@@ -15,15 +18,18 @@ def main(param1: int, param2: str, kw1=None, kw2=False):
 def test_opterate():
     doc, args = opterate(func=main)
     assert doc == "Example function with types documented in the docstring."
-    assert args == [
-        (['param1'], {'action': 'store', 'help': 'The first parameter.', 'type': int}),
-        (['param2'], {'action': 'store', 'help': 'The second parameter.', 'type': str}),
-        (
-            ['-k', '--kw1'],
-            {'action': 'store', 'default': None, 'dest': 'kw1', 'help': ''},
-        ),
-        (
-            ['-w', '--kw2'],
-            {'action': 'store_true', 'default': False, 'dest': 'kw2', 'help': '',},
-        ),
+    assert list(args) == ['param1', 'param2', 'kw1', 'kw2']
+
+    assert [v.flags for v in args.values()] == [
+        ['param1'],
+        ['param2'],
+        ['-k', '--kw1'],
+        ['-w', '--kw2'],
+    ]
+
+    assert [v.kwargs for v in args.values()] == [
+        {'action': 'store', 'help': 'The first parameter.', 'type': int,},
+        {'action': 'store', 'help': 'The second parameter.', 'type': str,},
+        {'action': 'store', 'default': None, 'dest': 'kw1', 'help': '',},
+        {'action': 'store_true', 'default': False, 'dest': 'kw2', 'help': '',},
     ]