diff --git a/mitmproxy/flow.py b/mitmproxy/flow.py
index 944c032d8..6a27a4a81 100644
--- a/mitmproxy/flow.py
+++ b/mitmproxy/flow.py
@@ -87,7 +87,7 @@ class Flow(stateobject.StateObject):
         type=str,
         intercepted=bool,
         marked=bool,
-        metadata=dict,
+        metadata=typing.Dict[str, typing.Any],
     )
 
     def get_state(self):
diff --git a/mitmproxy/stateobject.py b/mitmproxy/stateobject.py
index 007339e8c..ffaf285fa 100644
--- a/mitmproxy/stateobject.py
+++ b/mitmproxy/stateobject.py
@@ -1,18 +1,12 @@
-from typing import Any
-from typing import List
+import typing
+from typing import Any  # noqa
 from typing import MutableMapping  # noqa
 
 from mitmproxy.coretypes import serializable
-
-
-def _is_list(cls):
-    # The typing module is broken on Python 3.5.0, fixed on 3.5.1.
-    is_list_bugfix = getattr(cls, "__origin__", False) == getattr(List[Any], "__origin__", True)
-    return issubclass(cls, List) or is_list_bugfix
+from mitmproxy.utils import typecheck
 
 
 class StateObject(serializable.Serializable):
-
     """
     An object with serializable state.
 
@@ -34,22 +28,7 @@ class StateObject(serializable.Serializable):
         state = {}
         for attr, cls in self._stateobject_attributes.items():
             val = getattr(self, attr)
-            if val is None:
-                state[attr] = None
-            elif hasattr(val, "get_state"):
-                state[attr] = val.get_state()
-            elif _is_list(cls):
-                state[attr] = [x.get_state() for x in val]
-            elif isinstance(val, dict):
-                s = {}
-                for k, v in val.items():
-                    if hasattr(v, "get_state"):
-                        s[k] = v.get_state()
-                    else:
-                        s[k] = v
-                state[attr] = s
-            else:
-                state[attr] = val
+            state[attr] = get_state(cls, val)
         return state
 
     def set_state(self, state):
@@ -65,13 +44,51 @@ class StateObject(serializable.Serializable):
                 curr = getattr(self, attr)
                 if hasattr(curr, "set_state"):
                     curr.set_state(val)
-                elif hasattr(cls, "from_state"):
-                    obj = cls.from_state(val)
-                    setattr(self, attr, obj)
-                elif _is_list(cls):
-                    cls = cls.__parameters__[0] if cls.__parameters__ else cls.__args__[0]
-                    setattr(self, attr, [cls.from_state(x) for x in val])
-                else:  # primitive types such as int, str, ...
-                    setattr(self, attr, cls(val))
+                else:
+                    setattr(self, attr, make_object(cls, val))
         if state:
             raise RuntimeWarning("Unexpected State in __setstate__: {}".format(state))
+
+
+def _process(typeinfo: typecheck.Type, val: typing.Any, make: bool) -> typing.Any:
+    if val is None:
+        return None
+    elif make and hasattr(typeinfo, "from_state"):
+        return typeinfo.from_state(val)
+    elif not make and hasattr(val, "get_state"):
+        return val.get_state()
+
+    typename = str(typeinfo)
+
+    if typename.startswith("typing.List"):
+        T = typecheck.sequence_type(typeinfo)
+        return [_process(T, x, make) for x in val]
+    elif typename.startswith("typing.Tuple"):
+        Ts = typecheck.tuple_types(typeinfo)
+        if len(Ts) != len(val):
+            raise ValueError("Invalid data. Expected {}, got {}.".format(Ts, val))
+        return tuple(
+            _process(T, x, make) for T, x in zip(Ts, val)
+        )
+    elif typename.startswith("typing.Dict"):
+        k_cls, v_cls = typecheck.mapping_types(typeinfo)
+        return {
+            _process(k_cls, k, make): _process(v_cls, v, make)
+            for k, v in val.items()
+        }
+    elif typename.startswith("typing.Any"):
+        # FIXME: Remove this when we remove flow.metadata
+        assert isinstance(val, (int, str, bool, bytes))
+        return val
+    else:
+        return typeinfo(val)
+
+
+def make_object(typeinfo: typecheck.Type, val: typing.Any) -> typing.Any:
+    """Create an object based on the state given in val."""
+    return _process(typeinfo, val, True)
+
+
+def get_state(typeinfo: typecheck.Type, val: typing.Any) -> typing.Any:
+    """Get the state of the object given as val."""
+    return _process(typeinfo, val, False)
diff --git a/mitmproxy/utils/typecheck.py b/mitmproxy/utils/typecheck.py
index 1070fad08..22db68f58 100644
--- a/mitmproxy/utils/typecheck.py
+++ b/mitmproxy/utils/typecheck.py
@@ -1,7 +1,40 @@
 import typing
 
+Type = typing.Union[
+    typing.Any  # anything more elaborate really fails with mypy at the moment.
+]
 
-def check_option_type(name: str, value: typing.Any, typeinfo: typing.Any) -> None:
+
+def sequence_type(typeinfo: typing.Type[typing.List]) -> Type:
+    """Return the type of a sequence, e.g. typing.List"""
+    try:
+        return typeinfo.__args__[0]  # type: ignore
+    except AttributeError:  # Python 3.5.0
+        return typeinfo.__parameters__[0]  # type: ignore
+
+
+def tuple_types(typeinfo: typing.Type[typing.Tuple]) -> typing.Sequence[Type]:
+    """Return the types of a typing.Tuple"""
+    try:
+        return typeinfo.__args__  # type: ignore
+    except AttributeError:  # Python 3.5.x
+        return typeinfo.__tuple_params__  # type: ignore
+
+
+def union_types(typeinfo: typing.Type[typing.Tuple]) -> typing.Sequence[Type]:
+    """return the types of a typing.Union"""
+    try:
+        return typeinfo.__args__  # type: ignore
+    except AttributeError:  # Python 3.5.x
+        return typeinfo.__union_params__  # type: ignore
+
+
+def mapping_types(typeinfo: typing.Type[typing.Mapping]) -> typing.Tuple[Type, Type]:
+    """return the types of a mapping, e.g. typing.Dict"""
+    return typeinfo.__args__  # type: ignore
+
+
+def check_option_type(name: str, value: typing.Any, typeinfo: Type) -> None:
     """
     Check if the provided value is an instance of typeinfo and raises a
     TypeError otherwise. This function supports only those types required for
@@ -16,13 +49,7 @@ def check_option_type(name: str, value: typing.Any, typeinfo: typing.Any) -> Non
     typename = str(typeinfo)
 
     if typename.startswith("typing.Union"):
-        try:
-            types = typeinfo.__args__  # type: ignore
-        except AttributeError:
-            # Python 3.5.x
-            types = typeinfo.__union_params__  # type: ignore
-
-        for T in types:
+        for T in union_types(typeinfo):
             try:
                 check_option_type(name, value, T)
             except TypeError:
@@ -31,12 +58,7 @@ def check_option_type(name: str, value: typing.Any, typeinfo: typing.Any) -> Non
                 return
         raise e
     elif typename.startswith("typing.Tuple"):
-        try:
-            types = typeinfo.__args__  # type: ignore
-        except AttributeError:
-            # Python 3.5.x
-            types = typeinfo.__tuple_params__  # type: ignore
-
+        types = tuple_types(typeinfo)
         if not isinstance(value, (tuple, list)):
             raise e
         if len(types) != len(value):
@@ -45,11 +67,7 @@ def check_option_type(name: str, value: typing.Any, typeinfo: typing.Any) -> Non
             check_option_type("{}[{}]".format(name, i), x, T)
         return
     elif typename.startswith("typing.Sequence"):
-        try:
-            T = typeinfo.__args__[0]  # type: ignore
-        except AttributeError:
-            # Python 3.5.0
-            T = typeinfo.__parameters__[0]  # type: ignore
+        T = sequence_type(typeinfo)
         if not isinstance(value, (tuple, list)):
             raise e
         for v in value:
diff --git a/setup.cfg b/setup.cfg
index 7c7547228..592cc2e33 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -75,7 +75,6 @@ exclude =
     mitmproxy/proxy/protocol/tls.py
     mitmproxy/proxy/root_context.py
     mitmproxy/proxy/server.py
-    mitmproxy/stateobject.py
     mitmproxy/utils/bits.py
     pathod/language/actions.py
     pathod/language/base.py
diff --git a/test/mitmproxy/test_stateobject.py b/test/mitmproxy/test_stateobject.py
index d8c7a8e9b..bd5d17928 100644
--- a/test/mitmproxy/test_stateobject.py
+++ b/test/mitmproxy/test_stateobject.py
@@ -1,101 +1,146 @@
-from typing import List
+import typing
+
 import pytest
 
 from mitmproxy.stateobject import StateObject
 
 
-class Child(StateObject):
+class TObject(StateObject):
     def __init__(self, x):
         self.x = x
 
-    _stateobject_attributes = dict(
-        x=int
-    )
-
     @classmethod
     def from_state(cls, state):
         obj = cls(None)
         obj.set_state(state)
         return obj
 
+
+class Child(TObject):
+    _stateobject_attributes = dict(
+        x=int
+    )
+
     def __eq__(self, other):
         return isinstance(other, Child) and self.x == other.x
 
 
-class Container(StateObject):
-    def __init__(self):
-        self.child = None
-        self.children = None
-        self.dictionary = None
-
+class TTuple(TObject):
     _stateobject_attributes = dict(
-        child=Child,
-        children=List[Child],
-        dictionary=dict,
+        x=typing.Tuple[int, Child]
     )
 
-    @classmethod
-    def from_state(cls, state):
-        obj = cls()
-        obj.set_state(state)
-        return obj
+
+class TList(TObject):
+    _stateobject_attributes = dict(
+        x=typing.List[Child]
+    )
+
+
+class TDict(TObject):
+    _stateobject_attributes = dict(
+        x=typing.Dict[str, Child]
+    )
+
+
+class TAny(TObject):
+    _stateobject_attributes = dict(
+        x=typing.Any
+    )
+
+
+class TSerializableChild(TObject):
+    _stateobject_attributes = dict(
+        x=Child
+    )
 
 
 def test_simple():
     a = Child(42)
+    assert a.get_state() == {"x": 42}
     b = a.copy()
-    assert b.get_state() == {"x": 42}
     a.set_state({"x": 44})
     assert a.x == 44
     assert b.x == 42
 
 
-def test_container():
-    a = Container()
-    a.child = Child(42)
+def test_serializable_child():
+    child = Child(42)
+    a = TSerializableChild(child)
+    assert a.get_state() == {
+        "x": {"x": 42}
+    }
+    a.set_state({
+        "x": {"x": 43}
+    })
+    assert a.x.x == 43
+    assert a.x is child
     b = a.copy()
-    assert a.child.x == b.child.x
-    b.child.x = 44
-    assert a.child.x != b.child.x
+    assert a.x == b.x
+    assert a.x is not b.x
 
 
-def test_container_list():
-    a = Container()
-    a.children = [Child(42), Child(44)]
+def test_tuple():
+    a = TTuple((42, Child(43)))
     assert a.get_state() == {
-        "child": None,
-        "children": [{"x": 42}, {"x": 44}],
-        "dictionary": None,
+        "x": (42, {"x": 43})
+    }
+    b = a.copy()
+    a.set_state({"x": (44, {"x": 45})})
+    assert a.x == (44, Child(45))
+    assert b.x == (42, Child(43))
+
+
+def test_tuple_err():
+    a = TTuple(None)
+    with pytest.raises(ValueError, msg="Invalid data"):
+        a.set_state({"x": (42,)})
+
+
+def test_list():
+    a = TList([Child(1), Child(2)])
+    assert a.get_state() == {
+        "x": [{"x": 1}, {"x": 2}],
     }
     copy = a.copy()
-    assert len(copy.children) == 2
-    assert copy.children is not a.children
-    assert copy.children[0] is not a.children[0]
-    assert Container.from_state(a.get_state())
+    assert len(copy.x) == 2
+    assert copy.x is not a.x
+    assert copy.x[0] is not a.x[0]
 
 
-def test_container_dict():
-    a = Container()
-    a.dictionary = dict()
-    a.dictionary['foo'] = 'bar'
-    a.dictionary['bar'] = Child(44)
+def test_dict():
+    a = TDict({"foo": Child(42)})
     assert a.get_state() == {
-        "child": None,
-        "children": None,
-        "dictionary": {'bar': {'x': 44}, 'foo': 'bar'},
+        "x": {"foo": {"x": 42}}
     }
-    copy = a.copy()
-    assert len(copy.dictionary) == 2
-    assert copy.dictionary is not a.dictionary
-    assert copy.dictionary['bar'] is not a.dictionary['bar']
+    b = a.copy()
+    assert list(a.x.items()) == list(b.x.items())
+    assert a.x is not b.x
+    assert a.x["foo"] is not b.x["foo"]
+
+
+def test_any():
+    a = TAny(42)
+    b = a.copy()
+    assert a.x == b.x
+
+    a = TAny(object())
+    with pytest.raises(AssertionError):
+        a.get_state()
 
 
 def test_too_much_state():
-    a = Container()
-    a.child = Child(42)
+    a = Child(42)
     s = a.get_state()
     s['foo'] = 'bar'
-    b = Container()
 
     with pytest.raises(RuntimeWarning):
-        b.set_state(s)
+        a.set_state(s)
+
+
+def test_none():
+    a = Child(None)
+    assert a.get_state() == {"x": None}
+    a = Child(42)
+    a.set_state({"x": None})
+    assert a.x is None
diff --git a/test/mitmproxy/utils/test_typecheck.py b/test/mitmproxy/utils/test_typecheck.py
index 5295fff55..9cb4334e0 100644
--- a/test/mitmproxy/utils/test_typecheck.py
+++ b/test/mitmproxy/utils/test_typecheck.py
@@ -93,3 +93,8 @@ def test_typesec_to_str():
     assert(typecheck.typespec_to_str(typing.Optional[str])) == "optional str"
     with pytest.raises(NotImplementedError):
         typecheck.typespec_to_str(dict)
+
+
+def test_mapping_types():
+    # this is not covered by check_option_type, but still belongs in this module
+    assert (str, int) == typecheck.mapping_types(typing.Mapping[str, int])