diff --git a/k8sclient/client/api_client.py b/k8sclient/client/api_client.py
index dd7a62a..3cc60fb 100644
--- a/k8sclient/client/api_client.py
+++ b/k8sclient/client/api_client.py
@@ -40,6 +40,12 @@ from six.moves.urllib import parse as urlparse
 
 from .configuration import Configuration
 
+if six.PY3:
+    import io
+    file_type = io.IOBase
+else:
+    file_type = file
+
 
 class ApiClient(object):
     """
@@ -185,7 +191,8 @@ class ApiClient(object):
         """
         if isinstance(obj, type(None)):
             return None
-        elif isinstance(obj, (six.text_type, str, int, float, bool, tuple, file)):
+        elif isinstance(obj, (six.text_type, str, int, float,
+                              bool, tuple, file_type)):
             return obj
         elif isinstance(obj, list):
             return [self.sanitize_for_serialization(sub_obj)
diff --git a/requirements.txt b/requirements.txt
index 30ad9ef..69027a0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,4 +3,5 @@
 # process, which may cause wedges in the gate later.
 
 pbr>=1.6
+six>=1.9.0 # MIT
 urllib3>=1.8.3  # MIT
diff --git a/setup.cfg b/setup.cfg
index 6a50556..3199e03 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -16,7 +16,6 @@ classifier =
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.3
     Programming Language :: Python :: 3.4
 
 [files]