diff --git a/googleapiclient/discovery.py b/googleapiclient/discovery.py
index 6291f34..1266883 100644
--- a/googleapiclient/discovery.py
+++ b/googleapiclient/discovery.py
@@ -355,8 +355,9 @@
     scopes = list(
       service.get('auth', {}).get('oauth2', {}).get('scopes', {}).keys())
 
-    # If so, then the we need to setup authentication.
-    if scopes:
+    # If so, then the we need to setup authentication if no developerKey is
+    # specified.
+    if scopes and not developerKey:
       # If the user didn't pass in credentials, attempt to acquire application
       # default credentials.
       if credentials is None:
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
index 47adeb7..ec66bc6 100644
--- a/tests/test_discovery.py
+++ b/tests/test_discovery.py
@@ -437,6 +437,16 @@
       discovery, base="https://www.googleapis.com/", http=http)
     self.assertEquals(plus._http, http)
 
+  def test_building_with_developer_key_skips_adc(self):
+    discovery = open(datafile('plus.json')).read()
+    plus = build_from_document(
+      discovery, base="https://www.googleapis.com/", developerKey='123')
+    self.assertIsInstance(plus._http, httplib2.Http)
+    # It should not be an AuthorizedHttp, because that would indicate that
+    # application default credentials were used.
+    self.assertNotIsInstance(plus._http, google_auth_httplib2.AuthorizedHttp)
+
+
 class DiscoveryFromHttp(unittest.TestCase):
   def setUp(self):
     self.old_environ = os.environ.copy()