diff --git a/jsonrpc_async/jsonrpc.py b/jsonrpc_async/jsonrpc.py
index a9cfccf..c8ea942 100644
--- a/jsonrpc_async/jsonrpc.py
+++ b/jsonrpc_async/jsonrpc.py
@@ -9,7 +9,7 @@
 class Server(jsonrpc_base.Server):
     """A connection to a HTTP JSON-RPC server, backed by aiohttp"""
 
-    def __init__(self, url, session=None, **post_kwargs):
+    def __init__(self, url, session=None, *, loads=None, **post_kwargs):
         super().__init__()
         object.__setattr__(self, 'session', session or aiohttp.ClientSession())
         post_kwargs['headers'] = post_kwargs.get('headers', {})
@@ -19,6 +19,10 @@ def __init__(self, url, session=None, **post_kwargs):
             'Accept', 'application/json-rpc')
         self._request = functools.partial(self.session.post, url, **post_kwargs)
 
+        self._json_args = {}
+        if loads is not None:
+            self._json_args['loads'] = loads
+
     @asyncio.coroutine
     def send_message(self, message):
         """Send the HTTP message to the server and return the message response.
@@ -38,7 +42,7 @@ def send_message(self, message):
             return None
 
         try:
-            response_data = yield from response.json()
+            response_data = yield from response.json(**self._json_args)
         except ValueError as value_error:
             raise TransportError('Cannot deserialize response body', message, value_error)
 
diff --git a/tests.py b/tests.py
index ec395a0..93e01bd 100644
--- a/tests.py
+++ b/tests.py
@@ -1,8 +1,8 @@
 import asyncio
+from unittest import mock
 import unittest
 import random
 import json
-import inspect
 import os
 
 import aiohttp
@@ -15,11 +15,6 @@
 import jsonrpc_base
 from jsonrpc_async import Server, ProtocolError, TransportError
 
-try:
-    # python 3.3
-    from unittest.mock import Mock
-except ImportError:
-    from mock import Mock
 
 class JsonTestClient(aiohttp.test_utils.TestClient):
     def __init__(self, app, **kwargs):
@@ -31,6 +26,7 @@ def request(self, method, path, *args, **kwargs):
             self.request_callback(method, path, *args, **kwargs)
         return super().request(method, path, *args, **kwargs)
 
+
 class TestCase(unittest.TestCase):
     def assertSameJSON(self, json1, json2):
         """Tells whether two json strings, once decoded, are the same dictionary"""
@@ -40,8 +36,7 @@ def assertRaisesRegex(self, *args, **kwargs):
         return super(TestCase, self).assertRaisesRegex(*args, **kwargs)
 
 
-class TestJSONRPCClient(TestCase):
-
+class TestJSONRPCClientBase(TestCase):
     def setUp(self):
         self.loop = setup_test_loop()
         self.app = self.get_app()
@@ -53,8 +48,11 @@ def create_client(app, loop):
         self.client = self.loop.run_until_complete(
             create_client(self.app, self.loop))
         self.loop.run_until_complete(self.client.start_server())
-        random.randint = Mock(return_value=1)
-        self.server = Server('/xmlrpc', session=self.client, timeout=0.2)
+        random.randint = mock.Mock(return_value=1)
+        self.server = self.get_server()
+
+    def get_server(self):
+        return Server('/xmlrpc', session=self.client, timeout=0.2)
 
     def tearDown(self):
         self.loop.run_until_complete(self.client.close())
@@ -68,6 +66,8 @@ def response_func(request):
         app.router.add_post('/xmlrpc', response_func)
         return app
 
+
+class TestJSONRPCClient(TestJSONRPCClientBase):
     def test_pep8_conformance(self):
         """Test that we conform to PEP8."""
 
@@ -249,5 +249,25 @@ def handler(request):
         self.assertIsNone((yield from self.server.subtract(42, 23, _notification=True)))
 
 
+class TestJSONRPCClientCustomLoads(TestJSONRPCClientBase):
+    def get_server(self):
+        self.loads_mock = mock.Mock(wraps=json.loads)
+        return Server('/xmlrpc', session=self.client, loads=self.loads_mock, timeout=0.2)
+
+    @unittest_run_loop
+    @asyncio.coroutine
+    def test_custom_loads(self):
+        # rpc call with positional parameters:
+        @asyncio.coroutine
+        def handler1(request):
+            request_message = yield from request.json()
+            self.assertEqual(request_message["params"], [42, 23])
+            return aiohttp.web.Response(text='{"jsonrpc": "2.0", "result": 19, "id": 1}', content_type='application/json')
+
+        self.handler = handler1
+        self.assertEqual((yield from self.server.subtract(42, 23)), 19)
+        self.assertEqual(self.loads_mock.call_count, 1)
+
+
 if __name__ == '__main__':
     unittest.main()