diff --git a/odesk/namespaces.py b/odesk/namespaces.py
index 25c503c..3bc25f0 100644
--- a/odesk/namespaces.py
+++ b/odesk/namespaces.py
@@ -3,6 +3,7 @@
 # (C) 2010-2014 oDesk
 import os
 from .config import BASE_URL
+import posixpath
 
 __all__ = ['Namespace', 'GdsNamespace']
 
@@ -15,7 +16,7 @@ class Namespace(object):
 
     """
 
-    base_url = os.path.join(BASE_URL, 'api/')
+    base_url = posixpath.join(BASE_URL, 'api/')
     api_url = None
     version = 1
 
@@ -45,7 +46,7 @@ def delete(self, url, data=None):
 
 class GdsNamespace(Namespace):
     """Gds API only allows GET requests."""
-    base_url = os.path.join(BASE_URL, 'gds/')
+    base_url = posixpath.join(BASE_URL, 'gds/')
 
     def post(self, url, data=None):
         return None
diff --git a/odesk/oauth.py b/odesk/oauth.py
index e292de2..b16ca00 100644
--- a/odesk/oauth.py
+++ b/odesk/oauth.py
@@ -8,6 +8,7 @@
 import urllib
 import oauth2 as oauth
 import logging
+import posixpath
 
 from .config import BASE_URL
 
@@ -27,10 +28,10 @@ class OAuth(Namespace):
     api_url = 'auth/'
     version = 1
 
-    request_token_url = os.path.join(
+    request_token_url = posixpath.join(
         BASE_URL, 'api/auth/v1/oauth/token/request')
-    authorize_url = os.path.join(BASE_URL, 'services/api/auth')
-    access_token_url = os.path.join(BASE_URL, 'api/auth/v1/oauth/token/access')
+    authorize_url = posixpath.join(BASE_URL, 'services/api/auth')
+    access_token_url = posixpath.join(BASE_URL, 'api/auth/v1/oauth/token/access')
 
     def get_oauth_params(self, url, key, secret, data=None, method='GET',
                          to_header=False, to_dict=False):