diff --git a/src/attr/_make.py b/src/attr/_make.py
index f6eddefddd6aa07..e5310afbe8bfa92 100644
--- a/src/attr/_make.py
+++ b/src/attr/_make.py
@@ -7,6 +7,9 @@
 from ._compat import exec_, iteritems, isclass, iterkeys
 from .exceptions import FrozenInstanceError
 
+# This is used at least twice, so cache it here.
+_obj_setattr = object.__setattr__
+
 
 class _Nothing(object):
     """
@@ -414,7 +417,7 @@ def _add_init(cls, frozen):
     if frozen is True:
         # Save the lookup overhead in __init__ if we need to circumvent
         # immutability.
-        globs["_cached_setattr"] = object.__setattr__
+        globs["_cached_setattr"] = _obj_setattr
     exec_(bytecode, globs, locs)
     init = locs["__init__"]
 
@@ -596,17 +599,19 @@ class Attribute(object):
 
     _optional = {"convert": None}
 
-    def __init__(self, **kw):
-        if len(kw) > len(Attribute.__slots__):
-            raise TypeError("Too many arguments.")
-        for a in Attribute.__slots__:
-            try:
-                object.__setattr__(self, a, kw[a])
-            except KeyError:
-                if a in Attribute._optional:
-                    object.__setattr__(self, a, self._optional[a])
-                else:
-                    raise TypeError("Missing argument '{arg}'.".format(arg=a))
+    def __init__(self, name, default, validator, repr, cmp, hash, init,
+                 convert=None):
+        # Cache this descriptor here to speed things up later.
+        __bound_setattr = _obj_setattr.__get__(self, Attribute)
+
+        __bound_setattr('name', name)
+        __bound_setattr('default', default)
+        __bound_setattr('validator', validator)
+        __bound_setattr('repr', repr)
+        __bound_setattr('cmp', cmp)
+        __bound_setattr('hash', hash)
+        __bound_setattr('init', init)
+        __bound_setattr('convert', convert)
 
     def __setattr__(self, name, value):
         raise FrozenInstanceError()
diff --git a/tests/test_funcs.py b/tests/test_funcs.py
index 1216e431f4aa25d..404bcc9c2b6ed92 100644
--- a/tests/test_funcs.py
+++ b/tests/test_funcs.py
@@ -79,7 +79,8 @@ def assert_proper_dict_class(obj, obj_dict):
                     assert isinstance(obj_dict[field.name], dict_class)
                     for key, val in field_val.items():
                         if has(val.__class__):
-                            assert_proper_dict_class(val, obj_dict[key])
+                            assert_proper_dict_class(val,
+                                                     obj_dict[field.name][key])
 
         assert_proper_dict_class(obj, obj_dict)
 
diff --git a/tests/test_make.py b/tests/test_make.py
index bf1838e4661e95d..34e8af87c9087fc 100644
--- a/tests/test_make.py
+++ b/tests/test_make.py
@@ -13,7 +13,6 @@
 from attr._compat import PY2
 from attr._make import (
     Attribute,
-    NOTHING,
     _CountingAttr,
     _transform_attrs,
     attr,
@@ -294,29 +293,6 @@ class D(object):
         pass
 
 
-class TestAttribute(object):
-    """
-    Tests for `Attribute`.
-    """
-    def test_missing_argument(self):
-        """
-        Raises `TypeError` if an Argument is missing.
-        """
-        with pytest.raises(TypeError) as e:
-            Attribute(default=NOTHING, validator=None)
-        assert ("Missing argument 'name'.",) == e.value.args
-
-    def test_too_many_arguments(self):
-        """
-        Raises `TypeError` if extra arguments are passed.
-        """
-        with pytest.raises(TypeError) as e:
-            Attribute(name="foo", default=NOTHING,
-                      factory=NOTHING, validator=None,
-                      repr=True, cmp=True, hash=True, init=True, convert=None)
-        assert ("Too many arguments.",) == e.value.args
-
-
 class TestMakeClass(object):
     """
     Tests for `make_class`.
diff --git a/tests/utils.py b/tests/utils.py
index 568db6ab7be3689..e06cd597a8b0923 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -84,8 +84,9 @@ def _create_hyp_nested_strategy(simple_class_strategy):
     Create a recursive attrs class.
 
     Given a strategy for building (simpler) classes, create and return
-    a strategy for building classes that have the simpler class as an
-    attribute.
+    a strategy for building classes that have as an attribute: either just
+    the simpler class, a list of simpler classes, or a dict mapping the string
+    "cls" to a simpler class.
     """
     # Use a tuple strategy to combine simple attributes and an attr class.
     def just_class(tup):
@@ -105,10 +106,13 @@ def dict_of_class(tup):
         combined_attrs.append(attr.ib(default=default))
         return _create_hyp_class(combined_attrs)
 
-    return st.one_of(st.tuples(st.lists(simple_attrs), simple_class_strategy)
-                     .map(just_class),
-                     st.tuples(st.lists(simple_attrs), simple_class_strategy)
-                     .map(list_of_class))
+    # A strategy producing tuples of the form ([list of attributes], <given
+    # class strategy>).
+    attrs_and_classes = st.tuples(list_of_attrs, simple_class_strategy)
+
+    return st.one_of(attrs_and_classes.map(just_class),
+                     attrs_and_classes.map(list_of_class),
+                     attrs_and_classes.map(dict_of_class))
 
 bare_attrs = st.just(attr.ib(default=None))
 int_attrs = st.integers().map(lambda i: attr.ib(default=i))
@@ -121,8 +125,8 @@ def dict_of_class(tup):
                          dict_attrs)
 
 # Python functions support up to 255 arguments.
-simple_classes = (st.lists(simple_attrs, average_size=9, max_size=50)
-                  .map(_create_hyp_class))
+list_of_attrs = st.lists(simple_attrs, average_size=9, max_size=50)
+simple_classes = list_of_attrs.map(_create_hyp_class)
 
 # Ok, so st.recursive works by taking a base strategy (in this case,
 # simple_classes) and a special function. This function receives a strategy,