diff --git a/tests/test_builder.py b/tests/test_builder.py
index 55474714..62417464 100644
--- a/tests/test_builder.py
+++ b/tests/test_builder.py
@@ -67,18 +67,16 @@ def test_prepare_request(
 
 class TestCallFactory(object):
     def test_call(self, mocker, request_definition, request_builder):
-        instance = object()
         args = ()
         kwargs = {}
         request_preparer = mocker.Mock(spec=builder.RequestPreparer)
         request_preparer.create_request_builder.return_value = request_builder
         factory = builder.CallFactory(
-            instance,
             request_preparer,
             request_definition)
         assert factory(*args, **kwargs) is request_preparer.prepare_request.return_value
         request_definition.define_request.assert_called_with(
-            request_builder, (instance,) + args, kwargs
+            request_builder, args, kwargs
         )
         assert request_builder.build.called
 
diff --git a/tests/test_clients.py b/tests/test_clients.py
index 90e8276b..20a7ad3c 100644
--- a/tests/test_clients.py
+++ b/tests/test_clients.py
@@ -5,7 +5,7 @@
 import pytest
 
 # Local imports
-from uplink.clients import interfaces, requests_, twisted_, get_client
+from uplink.clients import interfaces, requests_, twisted_, register
 
 try:
     from uplink.clients import aiohttp_
@@ -17,12 +17,23 @@
     not aiohttp_, reason="Requires Python 3.4 or above")
 
 
+def test_get_default_client_with_non_callable(mocker):
+    # Setup
+    old_default = register.get_default_client()
+    register.set_default_client("client")
+    default_client = register.get_default_client()
+    register.set_default_client(old_default)
+
+    # Verify: an object that is not callable should be returned as set.
+    assert default_client == "client"
+
+
 def test_get_client_with_http_client_adapter_subclass():
     class HttpClientAdapterMock(interfaces.HttpClientAdapter):
         def create_request(self):
             pass
 
-    client = get_client(HttpClientAdapterMock)
+    client = register.get_client(HttpClientAdapterMock)
     assert isinstance(client, HttpClientAdapterMock)
 
 
@@ -31,7 +42,7 @@ class TestRequests(object):
     def test_get_client(self, mocker):
         import requests
         session_mock = mocker.Mock(spec=requests.Session)
-        client = get_client(session_mock)
+        client = register.get_client(session_mock)
         assert isinstance(client, requests_.RequestsClient)
 
 
@@ -93,7 +104,7 @@ class TestAiohttp(object):
 
     @requires_aiohttp
     def test_get_client(self, aiohttp_session_mock):
-        client = get_client(aiohttp_session_mock)
+        client = register.get_client(aiohttp_session_mock)
         assert isinstance(client, aiohttp_.AiohttpClient)
 
     @requires_aiohttp
diff --git a/uplink/builder.py b/uplink/builder.py
index cd739356..7b407343 100644
--- a/uplink/builder.py
+++ b/uplink/builder.py
@@ -78,13 +78,11 @@ def create_request_builder(self):
 
 
 class CallFactory(object):
-    def __init__(self, instance, request_preparer, request_definition):
-        self._instance = instance
+    def __init__(self, request_preparer, request_definition):
         self._request_preparer = request_preparer
         self._request_definition = request_definition
 
     def __call__(self, *args, **kwargs):
-        args = (self._instance,) + args
         builder = self._request_preparer.create_request_builder()
         self._request_definition.define_request(builder, args, kwargs)
         request = builder.build()
@@ -133,16 +131,12 @@ def add_converter(self, *converters_):
         self._converters.extendleft(converters_)
 
     @utils.memoize()
-    def build(self, consumer, definition):
+    def build(self, definition):
         """
         Creates a callable that uses the provided definition to execute
         HTTP requests when invoked.
         """
-        return CallFactory(
-            consumer,
-            RequestPreparer(self, definition),
-            definition
-        )
+        return CallFactory(RequestPreparer(self, definition), definition)
 
 
 class ConsumerMethod(object):
@@ -172,7 +166,7 @@ def __get__(self, instance, owner):
         if instance is None:
             return self._request_definition_builder
         else:
-            return instance._builder.build(instance, self._request_definition)
+            return instance._builder.build(self._request_definition)
 
 
 class ConsumerMeta(type):
diff --git a/uplink/types.py b/uplink/types.py
index 451004aa..6ba04cc7 100644
--- a/uplink/types.py
+++ b/uplink/types.py
@@ -137,8 +137,8 @@ def annotations(self):
     def get_relevant_arguments(self, call_args):
         return filter(call_args.__contains__, self._arguments)
 
-    def handle_call(self, request_builder, func_args, func_kwargs):
-        call_args = utils.get_call_args(self._func, *func_args, **func_kwargs)
+    def handle_call(self, request_builder, args, kwargs):
+        call_args = utils.get_call_args(self._func, None, *args, **kwargs)
         for name in self.get_relevant_arguments(call_args):
             self.handle_argument(
                 request_builder,