diff --git a/apns2/credentials.py b/apns2/credentials.py
index 4f2b813..5ea857a 100644
--- a/apns2/credentials.py
+++ b/apns2/credentials.py
@@ -57,7 +57,7 @@ class TokenCredentials(Credentials):
 
     @staticmethod
     def _is_expired_token(issue_date):
-        return time.time() < issue_date + DEFAULT_TOKEN_LIFETIME
+        return time.time() > issue_date + DEFAULT_TOKEN_LIFETIME
 
     @staticmethod
     def _get_signing_key(key_path):
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 895a1f0..9e428e6 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1 +1,2 @@
+freezegun
 mock; python_version < '3.3'
diff --git a/test/test_credentials.py b/test/test_credentials.py
index 180b9fb..e390da5 100644
--- a/test/test_credentials.py
+++ b/test/test_credentials.py
@@ -6,6 +6,8 @@
 
 from unittest import TestCase, main
 
+from freezegun import freeze_time
+
 import time
 
 from apns2.credentials import TokenCredentials
@@ -28,12 +30,14 @@ class TokenCredentialsTestCase(TestCase):
                                              self.team_id)
         self.lasting_header = self.normal_creds.get_authorization_header(
             self.topics[0])
-        self.expiring_creds = \
-            TokenCredentials(self.key_path, self.key_id,
-                             self.team_id,
-                             token_lifetime=self.token_lifetime)
-        self.expiring_header = self.expiring_creds.get_authorization_header(
-            self.topics[0])
+
+        with freeze_time('2012-01-14'):
+            self.expiring_creds = \
+                TokenCredentials(self.key_path, self.key_id,
+                                 self.team_id,
+                                 token_lifetime=self.token_lifetime)
+            self.expiring_header = self.expiring_creds.get_authorization_header(
+                self.topics[0])
 
     def test_create_multiple_topics(self):
         h1 = self.normal_creds.get_authorization_header(self.topics[0])
diff --git a/tox.ini b/tox.ini
index a63c8c7..f874560 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,8 +4,8 @@ envlist = py27, py34, py35, py36
 [testenv]
 commands = nosetests []
 
-deps = 
-	nose
-	py27: mock
+deps =
+    nose
+    -rrequirements-dev.txt
 
 usedevelop=True