diff --git a/apiclient/discovery.py b/apiclient/discovery.py
index eb179ff..1fc33ca 100644
--- a/apiclient/discovery.py
+++ b/apiclient/discovery.py
@@ -225,7 +225,9 @@
   document that is it given, as opposed to retrieving one over HTTP.
 
   Args:
-    service: string, discovery document.
+    service: string or object, the JSON discovery document describing the API.
+      The value passed in may either be the JSON string or the deserialized
+      JSON.
     base: string, base URI for all HTTP requests, usually the discovery URI.
       This parameter is no longer used as rootUrl and servicePath are included
       within the discovery document. (deprecated)
@@ -245,7 +247,8 @@
   # future is no longer used.
   future = {}
 
-  service = simplejson.loads(service)
+  if isinstance(service, basestring):
+    service = simplejson.loads(service)
   base = urlparse.urljoin(service['rootUrl'], service['servicePath'])
   schema = Schemas(service)
 
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
index b2ee56c..2c28cd2 100644
--- a/tests/test_discovery.py
+++ b/tests/test_discovery.py
@@ -125,6 +125,14 @@
     discovery = file(datafile('plus.json')).read()
     plus = build_from_document(discovery, base="https://www.googleapis.com/")
     self.assertTrue(plus is not None)
+    self.assertTrue(hasattr(plus, 'activities'))
+
+  def test_can_build_from_local_deserialized_document(self):
+    discovery = file(datafile('plus.json')).read()
+    discovery = simplejson.loads(discovery)
+    plus = build_from_document(discovery, base="https://www.googleapis.com/")
+    self.assertTrue(plus is not None)
+    self.assertTrue(hasattr(plus, 'activities'))
 
   def test_building_with_base_remembers_base(self):
     discovery = file(datafile('plus.json')).read()