diff --git a/openapi_core/media_types.py b/openapi_core/media_types.py
index a4a34f2..5c52834 100644
--- a/openapi_core/media_types.py
+++ b/openapi_core/media_types.py
@@ -1,9 +1,17 @@
 """OpenAPI core mediaTypes module"""
+from collections import defaultdict
+
+from json import loads
 from six import iteritems
 
 from openapi_core.exceptions import InvalidValueType, InvalidMediaTypeValue
 
 
+MEDIA_TYPE_DESERIALIZERS = {
+    'application/json': loads,
+}
+
+
 class MediaType(object):
     """Represents an OpenAPI MediaType."""
 
@@ -11,12 +19,29 @@ class MediaType(object):
         self.mimetype = mimetype
         self.schema = schema
 
+    def get_deserializer_mapping(self):
+        mapping = MEDIA_TYPE_DESERIALIZERS.copy()
+        return defaultdict(lambda: lambda x: x, mapping)
+
+    def get_dererializer(self):
+        mapping = self.get_deserializer_mapping()
+        return mapping[self.mimetype]
+
+    def deserialize(self, value):
+        deserializer = self.get_dererializer()
+        return deserializer(value)
+
     def unmarshal(self, value):
         if not self.schema:
             return value
 
         try:
-            return self.schema.unmarshal(value)
+            deserialized = self.deserialize(value)
+        except ValueError as exc:
+            raise InvalidMediaTypeValue(str(exc))
+
+        try:
+            return self.schema.unmarshal(deserialized)
         except InvalidValueType as exc:
             raise InvalidMediaTypeValue(str(exc))
 
diff --git a/openapi_core/schemas.py b/openapi_core/schemas.py
index 66793a6..a96c705 100644
--- a/openapi_core/schemas.py
+++ b/openapi_core/schemas.py
@@ -6,7 +6,6 @@ import warnings
 from distutils.util import strtobool
 from functools import lru_cache
 
-from json import loads
 from six import iteritems
 
 from openapi_core.enums import SchemaType, SchemaFormat
@@ -126,8 +125,8 @@ class Schema(object):
         return list(map(self.items.unmarshal, value))
 
     def _unmarshal_object(self, value):
-        if isinstance(value, (str, bytes)):
-            value = loads(value)
+        if not isinstance(value, (dict, )):
+            raise InvalidValueType("Value of {0} not an object".format(value))
 
         all_properties = self.get_all_properties()
         all_required_properties = self.get_all_required_properties()
diff --git a/tests/integration/data/v3.0/petstore.yaml b/tests/integration/data/v3.0/petstore.yaml
index 81fe7b1..ca54905 100644
--- a/tests/integration/data/v3.0/petstore.yaml
+++ b/tests/integration/data/v3.0/petstore.yaml
@@ -108,6 +108,21 @@ paths:
                 $ref: "#/components/schemas/PetData"
         default:
           $ref: "#/components/responses/ErrorResponse"
+  /tags:
+    get:
+      summary: List all tags
+      operationId: listTags
+      tags:
+        - tags
+      responses:
+        '200':
+          description: Expected response to a valid request
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/TagList"
+        default:
+          $ref: "#/components/responses/ErrorResponse"
 components:
   schemas:
     Address:
@@ -186,6 +201,10 @@ components:
       properties:
         data:
           $ref: "#/components/schemas/Pet"
+    TagList:
+      type: array
+      items:
+        $ref: "#/components/schemas/Tag"
     Error:
       type: object
       required:
diff --git a/tests/integration/test_petstore.py b/tests/integration/test_petstore.py
index e67a6ab..c181589 100644
--- a/tests/integration/test_petstore.py
+++ b/tests/integration/test_petstore.py
@@ -655,3 +655,27 @@ class TestPetstore(object):
 
         assert response_result.errors == []
         assert response_result.data == data_json
+
+    def test_get_tags(self, spec, response_validator):
+        host_url = 'http://petstore.swagger.io/v1'
+        path_pattern = '/v1/tags'
+
+        request = MockRequest(
+            host_url, 'GET', '/tags',
+            path_pattern=path_pattern,
+        )
+
+        parameters = request.get_parameters(spec)
+        body = request.get_body(spec)
+
+        assert parameters == {}
+        assert body is None
+
+        data_json = []
+        data = json.dumps(data_json)
+        response = MockResponse(data)
+
+        response_result = response_validator.validate(request, response)
+
+        assert response_result.errors == []
+        assert response_result.data == data_json
diff --git a/tests/integration/test_validators.py b/tests/integration/test_validators.py
index ab08bb5..d9816e2 100644
--- a/tests/integration/test_validators.py
+++ b/tests/integration/test_validators.py
@@ -4,6 +4,7 @@ import pytest
 from openapi_core.exceptions import (
     InvalidServer, InvalidOperation, MissingParameter,
     MissingBody, InvalidContentType, InvalidResponse, InvalidMediaTypeValue,
+    InvalidValue,
 )
 from openapi_core.shortcuts import create_spec
 from openapi_core.validators import RequestValidator, ResponseValidator
@@ -239,6 +240,26 @@ class TestResponseValidator(object):
         assert result.data is None
         assert result.headers == {}
 
+    def test_invalid_value(self, validator):
+        request = MockRequest(self.host_url, 'get', '/v1/tags')
+        response_json = {
+            'data': [
+                {
+                    'id': 1,
+                    'name': 'Sparky'
+                },
+            ],
+        }
+        response_data = json.dumps(response_json)
+        response = MockResponse(response_data)
+
+        result = validator.validate(request, response)
+
+        assert len(result.errors) == 1
+        assert type(result.errors[0]) == InvalidValue
+        assert result.data is None
+        assert result.headers == {}
+
     def test_get_pets(self, validator):
         request = MockRequest(self.host_url, 'get', '/v1/pets')
         response_json = {