diff --git a/src/github/AuthenticatedUser.py b/src/github/AuthenticatedUser.py
index 55cdd7f9..c5f6eb0a 100644
--- a/src/github/AuthenticatedUser.py
+++ b/src/github/AuthenticatedUser.py
@@ -148,7 +148,7 @@ class AuthenticatedUser( object ):
         return self.__url
 
     def add_to_emails( self, *emails ):
-        assert len( emails ) == 0 or isinstance( emails[ 0 ], ( str, unicode ) ), emails
+        assert all( isinstance( email, ( str, unicode ) ) for email in emails ), emails
         post_parameters = emails
         status, headers, data = self.__requester.request(
             "POST",
@@ -238,6 +238,8 @@ class AuthenticatedUser( object ):
             None,
             post_parameters
         )
+        if self.__requester.isFailureStatus( status ):
+            raise GithubException( status, data )
         return UserKey.UserKey( self.__requester, data, completion = NoCompletion )
 
     def create_repo( self, name, description = DefaultValueForOptionalParameters, homepage = DefaultValueForOptionalParameters, private = DefaultValueForOptionalParameters, has_issues = DefaultValueForOptionalParameters, has_wiki = DefaultValueForOptionalParameters, has_downloads = DefaultValueForOptionalParameters ):
diff --git a/src/github/GithubObject.py b/src/github/GithubObject.py
index e36123a7..55ae0e62 100644
--- a/src/github/GithubObject.py
+++ b/src/github/GithubObject.py
@@ -6,3 +6,9 @@ DefaultValueForOptionalParameters = DefaultValueForOptionalParametersType()
 LazyCompletion = 0
 ImmediateCompletion = 1
 NoCompletion = 2
+
+class GithubException( Exception ):
+    def __init__( self, status, data ):
+        Exception.__init__( self )
+        self.status = status
+        self.data = data
diff --git a/src/github/Requester.py b/src/github/Requester.py
index 8ccb30b8..06f3f430 100644
--- a/src/github/Requester.py
+++ b/src/github/Requester.py
@@ -3,9 +3,6 @@ import json
 import base64
 import urllib
 
-class UnknownGithubObject( Exception ):
-    pass
-
 class Requester:
     def __init__( self, login_or_token, password ):
         if password is not None:
@@ -61,3 +58,6 @@ class Requester:
 
     def parentUrl( self, url ):
         return "/".join( url.split( "/" )[ : -1 ] )
+
+    def isFailureStatus( self, status ):
+        return status >= 400
diff --git a/src/github/__init__.py b/src/github/__init__.py
index 109d6b9a..392e4617 100644
--- a/src/github/__init__.py
+++ b/src/github/__init__.py
@@ -1 +1,2 @@
 from Github import Github
+from GithubObject import GithubException
diff --git a/test/Exceptions.py b/test/Exceptions.py
new file mode 100644
index 00000000..0f83c9d8
--- /dev/null
+++ b/test/Exceptions.py
@@ -0,0 +1,23 @@
+import github
+
+import Framework
+
+class Exceptions( Framework.TestCase ):
+    def testInvalidInput( self ):
+        with self.assertRaises( github.GithubException ) as cm:
+            self.g.get_user().create_key( "Bad key", "xxx" )
+        self.assertEqual( cm.exception.status, 422 )
+        self.assertEqual(
+            cm.exception.data,
+            { 
+                "errors": [
+                    {
+                        "code": "custom",
+                        "field": "key",
+                        "message": "key is invalid. It must begin with 'ssh-rsa' or 'ssh-dss'. Check that you're copying the public half of the key",
+                        "resource": "PublicKey"
+                    }
+                ],
+                "message": "Validation Failed"
+            }
+        )
diff --git a/test/IntegrationTest.py b/test/IntegrationTest.py
index f2a0b279..4a3eaf89 100644
--- a/test/IntegrationTest.py
+++ b/test/IntegrationTest.py
@@ -38,5 +38,6 @@ from UserKey import *
 
 from PaginatedList import *
 from Issue33 import *
+from Exceptions import *
 
 Framework.main()
diff --git a/test/ReplayData/Exceptions.testInvalidInput.txt b/test/ReplayData/Exceptions.testInvalidInput.txt
new file mode 100644
index 00000000..44ce6375
--- /dev/null
+++ b/test/ReplayData/Exceptions.testInvalidInput.txt
@@ -0,0 +1,5 @@
+POST /user/keys {'Authorization': 'Basic login_and_password_removed'} {"key": "xxx", "title": "Bad key"}
+422
+[('status', '422 Unprocessable Entity'), ('x-ratelimit-remaining', '4995'), ('content-length', '221'), ('server', 'nginx/1.0.13'), ('connection', 'keep-alive'), ('x-ratelimit-limit', '5000'), ('etag', '"73f756ef75655dd74463eb1bf4cfefe1"'), ('date', 'Wed, 30 May 2012 07:00:27 GMT'), ('content-type', 'application/json; charset=utf-8')]
+{"message":"Validation Failed","errors":[{"field":"key","resource":"PublicKey","message":"key is invalid. It must begin with 'ssh-rsa' or 'ssh-dss'. Check that you're copying the public half of the key","code":"custom"}]}
+