diff --git a/oauth2client/client.py b/oauth2client/client.py
index f492563..c88b358 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -55,6 +55,9 @@
 # Which certs to use to validate id_tokens received.
 ID_TOKEN_VERIFICATON_CERTS = 'https://www.googleapis.com/oauth2/v1/certs'
 
+# Constant to use for the out of band OAuth 2.0 flow.
+OOB_CALLBACK_URN = 'urn:ietf:wg:oauth:2.0:oob'
+
 
 class Error(Exception):
   """Base error for this module."""
@@ -843,15 +846,15 @@
     self.params.update(kwargs)
     self.redirect_uri = None
 
-  def step1_get_authorize_url(self, redirect_uri='oob'):
+  def step1_get_authorize_url(self, redirect_uri=OOB_CALLBACK_URN):
     """Returns a URI to redirect to the provider.
 
     Args:
-      redirect_uri: string, Either the string 'oob' for a non-web-based
-                    application, or a URI that handles the callback from
-                    the authorization server.
+      redirect_uri: string, Either the string 'urn:ietf:wg:oauth:2.0:oob' for
+          a non-web-based application, or a URI that handles the callback from
+          the authorization server.
 
-    If redirect_uri is 'oob' then pass in the
+    If redirect_uri is 'urn:ietf:wg:oauth:2.0:oob' then pass in the
     generated verification code to step2_exchange,
     otherwise pass in the query parameters received
     at the callback uri to step2_exchange.
diff --git a/oauth2client/tools.py b/oauth2client/tools.py
index 236c859..eeb9031 100644
--- a/oauth2client/tools.py
+++ b/oauth2client/tools.py
@@ -30,6 +30,7 @@
 import webbrowser
 
 from client import FlowExchangeError
+from client import OOB_CALLBACK_URN
 
 try:
   from urlparse import parse_qsl
@@ -120,7 +121,7 @@
   if FLAGS.auth_local_webserver:
     oauth_callback = 'http://%s:%s/' % (FLAGS.auth_host_name, port_number)
   else:
-    oauth_callback = 'oob'
+    oauth_callback = OOB_CALLBACK_URN
   authorize_url = flow.step1_get_authorize_url(oauth_callback)
 
   if FLAGS.auth_local_webserver:
diff --git a/tests/test_oauth2client.py b/tests/test_oauth2client.py
index dfcbf72..d50d6a0 100644
--- a/tests/test_oauth2client.py
+++ b/tests/test_oauth2client.py
@@ -42,6 +42,7 @@
 from oauth2client.client import FlowExchangeError
 from oauth2client.client import OAuth2Credentials
 from oauth2client.client import OAuth2WebServerFlow
+from oauth2client.client import OOB_CALLBACK_URN
 from oauth2client.client import VerifyJwtTokenError
 from oauth2client.client import _extract_id_token
 
@@ -196,14 +197,14 @@
         )
 
   def test_construct_authorize_url(self):
-    authorize_url = self.flow.step1_get_authorize_url('oob')
+    authorize_url = self.flow.step1_get_authorize_url('OOB_CALLBACK_URN')
 
     parsed = urlparse.urlparse(authorize_url)
     q = parse_qs(parsed[4])
     self.assertEqual(q['client_id'][0], 'client_id+1')
     self.assertEqual(q['response_type'][0], 'code')
     self.assertEqual(q['scope'][0], 'foo')
-    self.assertEqual(q['redirect_uri'][0], 'oob')
+    self.assertEqual(q['redirect_uri'][0], 'OOB_CALLBACK_URN')
     self.assertEqual(q['access_type'][0], 'offline')
 
   def test_override_flow_access_type(self):
@@ -215,14 +216,14 @@
         user_agent='unittest-sample/1.0',
         access_type='online'
         )
-    authorize_url = flow.step1_get_authorize_url('oob')
+    authorize_url = flow.step1_get_authorize_url('OOB_CALLBACK_URN')
 
     parsed = urlparse.urlparse(authorize_url)
     q = parse_qs(parsed[4])
     self.assertEqual(q['client_id'][0], 'client_id+1')
     self.assertEqual(q['response_type'][0], 'code')
     self.assertEqual(q['scope'][0], 'foo')
-    self.assertEqual(q['redirect_uri'][0], 'oob')
+    self.assertEqual(q['redirect_uri'][0], 'OOB_CALLBACK_URN')
     self.assertEqual(q['access_type'][0], 'online')
 
   def test_exchange_failure(self):