diff --git a/googleapiclient/discovery_cache/file_cache.py b/googleapiclient/discovery_cache/file_cache.py
index e88e7dc..48bddea 100644
--- a/googleapiclient/discovery_cache/file_cache.py
+++ b/googleapiclient/discovery_cache/file_cache.py
@@ -36,9 +36,9 @@
   try:
     from oauth2client.locked_file import LockedFile
   except ImportError:
-    # oauth2client > 4.0.0
+    # oauth2client > 4.0.0 or google-auth
     raise ImportError(
-      'file_cache is unavailable when using oauth2client >= 4.0.0')
+      'file_cache is unavailable when using oauth2client >= 4.0.0 or google-auth')
 
 from . import base
 from ..discovery_cache import DISCOVERY_DOC_MAX_AGE
diff --git a/setup.py b/setup.py
index 4796840..07a4440 100644
--- a/setup.py
+++ b/setup.py
@@ -64,7 +64,8 @@
 
 install_requires = [
     'httplib2>=0.9.2,<1dev',
-    'oauth2client>=1.5.0,<5.0.0dev',
+    'google-auth>=1.4.1',
+    'google-auth-httplib2>=0.0.3',
     'six>=1.6.1,<2dev',
     'uritemplate>=3.0.0,<4dev',
 ]
diff --git a/tests/__init__.py b/tests/__init__.py
index 8f6d06b..d88353f 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -16,12 +16,7 @@
 __author__ = 'afshar@google.com (Ali Afshar)'
 
 
-# Oauth2client < 3 has the positional helper in 'util', >= 3 has it
-# in '_helpers'.
-try:
-  from oauth2client import util
-except ImportError:
-  from oauth2client import _helpers as util
+from googleapiclient import _helpers as util
 
 
 def setup_package():