diff --git a/.travis.yml b/.travis.yml
index f80f2790..b2d8c50c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,9 +2,9 @@ language: python
 sudo: false
 python:
 - 2.7
-- 3.3
 - 3.4
 - 3.5
+- 3.6
 - pypy
 before_install:
 - |
diff --git a/graphql/__init__.py b/graphql/__init__.py
index d53457d4..a01711ba 100644
--- a/graphql/__init__.py
+++ b/graphql/__init__.py
@@ -202,6 +202,9 @@
 
         # Asserts a string is a valid GraphQL name.
         assert_valid_name,
+
+        # Undefined const
+        Undefined,
     )
 
     __all__ = (
@@ -284,4 +287,5 @@
         'type_from_ast',
         'value_from_ast',
         'get_version',
+        'Undefined',
     )
diff --git a/graphql/execution/base.py b/graphql/execution/base.py
index 04b3629d..ca23fed9 100644
--- a/graphql/execution/base.py
+++ b/graphql/execution/base.py
@@ -4,7 +4,7 @@
 from ..error import GraphQLError
 from ..language import ast
 from ..pyutils.default_ordered_dict import DefaultOrderedDict
-from ..type.definition import Undefined, GraphQLInterfaceType, GraphQLUnionType
+from ..type.definition import GraphQLInterfaceType, GraphQLUnionType
 from ..type.directives import GraphQLIncludeDirective, GraphQLSkipDirective
 from ..type.introspection import (SchemaMetaFieldDef, TypeMetaFieldDef,
                                   TypeNameMetaFieldDef)
@@ -75,7 +75,6 @@ def get_field_resolver(self, field_resolver):
     def get_argument_values(self, field_def, field_ast):
         k = field_def, field_ast
         result = self.argument_values_cache.get(k)
-
         if not result:
             result = self.argument_values_cache[k] = get_argument_values(field_def.args, field_ast.arguments,
                                                                          self.variable_values)
diff --git a/graphql/execution/executor.py b/graphql/execution/executor.py
index 797c2fd7..699ba8e7 100644
--- a/graphql/execution/executor.py
+++ b/graphql/execution/executor.py
@@ -9,10 +9,11 @@
 from ..error import GraphQLError, GraphQLLocatedError
 from ..pyutils.default_ordered_dict import DefaultOrderedDict
 from ..pyutils.ordereddict import OrderedDict
+from ..utils.undefined import Undefined
 from ..type import (GraphQLEnumType, GraphQLInterfaceType, GraphQLList,
                     GraphQLNonNull, GraphQLObjectType, GraphQLScalarType,
                     GraphQLSchema, GraphQLUnionType)
-from .base import (ExecutionContext, ExecutionResult, ResolveInfo, Undefined,
+from .base import (ExecutionContext, ExecutionResult, ResolveInfo,
                    collect_fields, default_resolve_fn, get_field_def,
                    get_operation_root_type)
 from .executors.sync import SyncExecutor
diff --git a/graphql/execution/experimental/fragment.py b/graphql/execution/experimental/fragment.py
index 427acbaf..d6b75120 100644
--- a/graphql/execution/experimental/fragment.py
+++ b/graphql/execution/experimental/fragment.py
@@ -4,9 +4,10 @@
 
 from ...pyutils.cached_property import cached_property
 from ...pyutils.default_ordered_dict import DefaultOrderedDict
+from ...utils.undefined import Undefined
 from ...type import (GraphQLInterfaceType, GraphQLList, GraphQLNonNull,
                      GraphQLObjectType, GraphQLUnionType)
-from ..base import ResolveInfo, Undefined, collect_fields, get_field_def
+from ..base import ResolveInfo, collect_fields, get_field_def
 from ..values import get_argument_values
 from ...error import GraphQLError
 try:
diff --git a/graphql/execution/experimental/tests/test_variables.py b/graphql/execution/experimental/tests/test_variables.py
index 83e91a22..0bafa260 100644
--- a/graphql/execution/experimental/tests/test_variables.py
+++ b/graphql/execution/experimental/tests/test_variables.py
@@ -413,9 +413,10 @@ def test_passes_along_null_for_non_nullable_inputs_if_explcitly_set_in_the_query
     '''
 
     check(doc, {
-        'data': {
-            'fieldWithNonNullableStringInput': None
-        }
+        'errors': [{
+            'message': 'Argument "input" of required type String!" was not provided.'
+        }],
+        'data': None
     })
 
 
diff --git a/graphql/execution/tests/test_variables.py b/graphql/execution/tests/test_variables.py
index 83e91a22..36d0ba1a 100644
--- a/graphql/execution/tests/test_variables.py
+++ b/graphql/execution/tests/test_variables.py
@@ -6,7 +6,7 @@
 from graphql.error import GraphQLError, format_error
 from graphql.execution import execute
 from graphql.language.parser import parse
-from graphql.type import (GraphQLArgument, GraphQLField,
+from graphql.type import (GraphQLArgument, GraphQLField, GraphQLBoolean,
                           GraphQLInputObjectField, GraphQLInputObjectType,
                           GraphQLList, GraphQLNonNull, GraphQLObjectType,
                           GraphQLScalarType, GraphQLSchema, GraphQLString)
@@ -18,6 +18,11 @@
     parse_literal=lambda v: 'DeserializedValue' if v.value == 'SerializedValue' else None
 )
 
+
+class my_special_dict(dict):
+    pass
+
+
 TestInputObject = GraphQLInputObjectType('TestInputObject', OrderedDict([
     ('a', GraphQLInputObjectField(GraphQLString)),
     ('b', GraphQLInputObjectField(GraphQLList(GraphQLString))),
@@ -25,6 +30,11 @@
     ('d', GraphQLInputObjectField(TestComplexScalar))
 ]))
 
+
+TestCustomInputObject = GraphQLInputObjectType('TestCustomInputObject', OrderedDict([
+    ('a', GraphQLInputObjectField(GraphQLString)),
+]), container_type=my_special_dict)
+
 stringify = lambda obj: json.dumps(obj, sort_keys=True)
 
 
@@ -47,6 +57,10 @@ def input_to_json(obj, args, context, info):
         GraphQLString,
         args={'input': GraphQLArgument(TestInputObject)},
         resolver=input_to_json),
+    'fieldWithCustomObjectInput': GraphQLField(
+        GraphQLBoolean,
+        args={'input': GraphQLArgument(TestCustomInputObject)},
+        resolver=lambda root, args, context, info: isinstance(args.get('input'), my_special_dict)),
     'fieldWithNullableStringInput': GraphQLField(
         GraphQLString,
         args={'input': GraphQLArgument(GraphQLString)},
@@ -412,9 +426,24 @@ def test_passes_along_null_for_non_nullable_inputs_if_explcitly_set_in_the_query
     }
     '''
 
+    check(doc, {
+        'errors': [{
+            'message': 'Argument "input" of required type String!" was not provided.'
+        }],
+        'data': None
+    })
+
+
+def test_uses_objectinput_container():
+    doc = '''
+    {
+        fieldWithCustomObjectInput(input: {a: "b"})
+    }
+    '''
+
     check(doc, {
         'data': {
-            'fieldWithNonNullableStringInput': None
+            'fieldWithCustomObjectInput': True
         }
     })
 
diff --git a/graphql/execution/values.py b/graphql/execution/values.py
index 56008463..252ba1f3 100644
--- a/graphql/execution/values.py
+++ b/graphql/execution/values.py
@@ -4,6 +4,7 @@
 from six import string_types
 
 from ..error import GraphQLError
+from ..language import ast
 from ..language.printer import print_ast
 from ..type import (GraphQLEnumType, GraphQLInputObjectType, GraphQLList,
                     GraphQLNonNull, GraphQLScalarType, is_input_type)
@@ -23,8 +24,43 @@ def get_variable_values(schema, definition_asts, inputs):
     values = {}
     for def_ast in definition_asts:
         var_name = def_ast.variable.name.value
-        value = get_variable_value(schema, def_ast, inputs.get(var_name))
-        values[var_name] = value
+        var_type = type_from_ast(schema, def_ast.type)
+        value = inputs.get(var_name)
+
+        if not is_input_type(var_type):
+            raise GraphQLError(
+                'Variable "${var_name}" expected value of type "{var_type}" which cannot be used as an input type.'.format(
+                    var_name=var_name,
+                    var_type=print_ast(def_ast.type),
+                ),
+                [def_ast]
+            )
+        elif value is None:
+            if def_ast.default_value is not None:
+                values[var_name] = value_from_ast(def_ast.default_value, var_type)
+            if isinstance(var_type, GraphQLNonNull):
+                raise GraphQLError(
+                    'Variable "${var_name}" of required type "{var_type}" was not provided.'.format(
+                        var_name=var_name, var_type=var_type
+                    ), [def_ast]
+                )
+        else:
+            errors = is_valid_value(value, var_type)
+            if errors:
+                message = u'\n' + u'\n'.join(errors)
+                raise GraphQLError(
+                    'Variable "${}" got invalid value {}.{}'.format(
+                        var_name,
+                        json.dumps(value, sort_keys=True),
+                        message
+                    ),
+                    [def_ast]
+                )
+            coerced_value = coerce_value(var_type, value)
+            if coerced_value is None:
+                raise Exception('Should have reported error.')
+
+            values[var_name] = coerced_value
 
     return values
 
@@ -42,72 +78,52 @@ def get_argument_values(arg_defs, arg_asts, variables=None):
 
     result = {}
     for name, arg_def in arg_defs.items():
+        arg_type = arg_def.type
         value_ast = arg_ast_map.get(name)
-        if value_ast:
-            value_ast = value_ast.value
-
-        value = value_from_ast(
-            value_ast,
-            arg_def.type,
-            variables
-        )
+        if name not in arg_ast_map:
+            if arg_def.default_value is not None:
+                result[arg_def.out_name or name] = arg_def.default_value
+                continue
+            elif isinstance(arg_type, GraphQLNonNull):
+                raise GraphQLError('Argument "{name}" of required type {arg_type}" was not provided.'.format(
+                    name=name,
+                    arg_type=arg_type
+                ), arg_asts)
+        elif isinstance(value_ast.value, ast.Variable):
+            variable_name = value_ast.value.name.value
+            variable_value = variables.get(variable_name)
+            if variables and variable_name in variables:
+                result[arg_def.out_name or name] = variable_value
+            elif arg_def.default_value is not None:
+                result[arg_def.out_name or name] = arg_def.default_value
+            elif isinstance(arg_type, GraphQLNonNull):
+                raise GraphQLError('Argument "{name}" of required type {arg_type}" provided the variable "${variable_name}" which was not provided'.format(
+                    name=name,
+                    arg_type=arg_type,
+                    variable_name=variable_name
+                ), arg_asts)
+            continue
 
-        if value is None:
-            value = arg_def.default_value
+        else:
+            value_ast = value_ast.value
 
-        if value is not None:
-            # We use out_name as the output name for the
-            # dict if exists
-            result[arg_def.out_name or name] = value
+            value = value_from_ast(
+                value_ast,
+                arg_type,
+                variables
+            )
+            if value is None:
+                if arg_def.default_value is not None:
+                    value = arg_def.default_value
+                    result[arg_def.out_name or name] = value
+            else:
+                # We use out_name as the output name for the
+                # dict if exists
+                result[arg_def.out_name or name] = value
 
     return result
 
 
-def get_variable_value(schema, definition_ast, input):
-    """Given a variable definition, and any value of input, return a value which adheres to the variable definition,
-    or throw an error."""
-    type = type_from_ast(schema, definition_ast.type)
-    variable = definition_ast.variable
-
-    if not type or not is_input_type(type):
-        raise GraphQLError(
-            'Variable "${}" expected value of type "{}" which cannot be used as an input type.'.format(
-                variable.name.value,
-                print_ast(definition_ast.type),
-            ),
-            [definition_ast]
-        )
-
-    input_type = type
-    errors = is_valid_value(input, input_type)
-    if not errors:
-        if input is None:
-            default_value = definition_ast.default_value
-            if default_value:
-                return value_from_ast(default_value, input_type)
-
-        return coerce_value(input_type, input)
-
-    if input is None:
-        raise GraphQLError(
-            'Variable "${}" of required type "{}" was not provided.'.format(
-                variable.name.value,
-                print_ast(definition_ast.type)
-            ),
-            [definition_ast]
-        )
-
-    message = (u'\n' + u'\n'.join(errors)) if errors else u''
-    raise GraphQLError(
-        'Variable "${}" got invalid value {}.{}'.format(
-            variable.name.value,
-            json.dumps(input, sort_keys=True),
-            message
-        ),
-        [definition_ast]
-    )
-
-
 def coerce_value(type, value):
     """Given a type and any value, return a runtime value coerced to match the type."""
     if isinstance(type, GraphQLNonNull):
@@ -130,16 +146,15 @@ def coerce_value(type, value):
         fields = type.fields
         obj = {}
         for field_name, field in fields.items():
-            field_value = coerce_value(field.type, value.get(field_name))
-            if field_value is None:
-                field_value = field.default_value
-
-            if field_value is not None:
-                # We use out_name as the output name for the
-                # dict if exists
+            if field_name not in value:
+                if field.default_value is not None:
+                    field_value = field.default_value
+                    obj[field.out_name or field_name] = field_value
+            else:
+                field_value = coerce_value(field.type, value.get(field_name))
                 obj[field.out_name or field_name] = field_value
 
-        return obj
+        return type.create_container(obj)
 
     assert isinstance(type, (GraphQLScalarType, GraphQLEnumType)), \
         'Must be input type'
diff --git a/graphql/type/__init__.py b/graphql/type/__init__.py
index 6f53635d..153c1b5e 100644
--- a/graphql/type/__init__.py
+++ b/graphql/type/__init__.py
@@ -19,8 +19,7 @@
     is_leaf_type,
     is_type,
     get_nullable_type,
-    is_output_type,
-    Undefined
+    is_output_type
 )
 from .directives import (
     # "Enum" of Directive locations
diff --git a/graphql/type/definition.py b/graphql/type/definition.py
index 24cee3b1..e593fb23 100644
--- a/graphql/type/definition.py
+++ b/graphql/type/definition.py
@@ -7,16 +7,6 @@
 from ..utils.assert_valid_name import assert_valid_name
 
 
-class _Undefined(object):
-    def __bool__(self):
-        return False
-
-    __nonzero__ = __bool__
-
-
-Undefined = _Undefined()
-
-
 def is_type(type):
     return isinstance(type, (
         GraphQLScalarType,
@@ -516,13 +506,19 @@ class GeoPoint(GraphQLInputObjectType):
                     default_value=0)
             }
     """
-    def __init__(self, name, fields, description=None):
+    def __init__(self, name, fields, description=None, container_type=None):
         assert name, 'Type must be named.'
         self.name = name
         self.description = description
-
+        if container_type is None:
+            container_type = dict
+        assert callable(container_type), "container_type must be callable"
+        self.container_type = container_type
         self._fields = fields
 
+    def create_container(self, data):
+        return self.container_type(data)
+
     @cached_property
     def fields(self):
         return self._define_field_map()
diff --git a/graphql/utils/base.py b/graphql/utils/base.py
index 5e895853..54a10346 100644
--- a/graphql/utils/base.py
+++ b/graphql/utils/base.py
@@ -53,6 +53,10 @@
 # Asserts that a string is a valid GraphQL name
 from .assert_valid_name import assert_valid_name
 
+# Undefined const
+from .undefined import Undefined
+
+
 __all__ = [
     'introspection_query',
     'get_operation_ast',
@@ -72,4 +76,5 @@
     'is_equal_type',
     'is_type_sub_type_of',
     'assert_valid_name',
+    'Undefined',
 ]
diff --git a/graphql/utils/undefined.py b/graphql/utils/undefined.py
new file mode 100644
index 00000000..00e47835
--- /dev/null
+++ b/graphql/utils/undefined.py
@@ -0,0 +1,11 @@
+class _Undefined(object):
+    def __bool__(self):
+        return False
+
+    __nonzero__ = __bool__
+
+    def __repr__(self):
+        return 'Undefined'
+
+
+Undefined = _Undefined()
diff --git a/graphql/utils/value_from_ast.py b/graphql/utils/value_from_ast.py
index ff7486be..55026680 100644
--- a/graphql/utils/value_from_ast.py
+++ b/graphql/utils/value_from_ast.py
@@ -11,7 +11,7 @@ def value_from_ast(value_ast, type, variables=None):
         # We're assuming that this query has been validated and the value used here is of the correct type.
         return value_from_ast(value_ast, type.of_type, variables)
 
-    if not value_ast:
+    if value_ast is None:
         return None
 
     if isinstance(value_ast, ast.Variable):
@@ -21,7 +21,7 @@ def value_from_ast(value_ast, type, variables=None):
 
         # Note: we're not doing any checking that this variable is correct. We're assuming that this query
         # has been validated and the variable usage here is of the correct type.
-        return variables[variable_name]
+        return variables.get(variable_name)
 
     if isinstance(type, GraphQLList):
         item_type = type.of_type
@@ -44,24 +44,25 @@ def value_from_ast(value_ast, type, variables=None):
 
         obj = {}
         for field_name, field in fields.items():
-            field_ast = field_asts.get(field_name)
-            field_value_ast = None
+            if field_name not in field_asts:
+                if field.default_value is not None:
+                    # We use out_name as the output name for the
+                    # dict if exists
+                    obj[field.out_name or field_name] = field.default_value
 
-            if field_ast:
-                field_value_ast = field_ast.value
+                continue
 
+            field_ast = field_asts.get(field_name)
+            field_value_ast = field_ast.value
             field_value = value_from_ast(
                 field_value_ast, field.type, variables
             )
-            if field_value is None:
-                field_value = field.default_value
 
-            if field_value is not None:
-                # We use out_name as the output name for the
-                # dict if exists
-                obj[field.out_name or field_name] = field_value
+            # We use out_name as the output name for the
+            # dict if exists
+            obj[field.out_name or field_name] = field_value
 
-        return obj
+        return type.create_container(obj)
 
     assert isinstance(type, (GraphQLScalarType, GraphQLEnumType)), \
         'Must be input type'