diff --git a/tests/integration/test_tornado.py b/tests/integration/test_tornado.py
index 7116256..3ef662e 100644
--- a/tests/integration/test_tornado.py
+++ b/tests/integration/test_tornado.py
@@ -278,7 +278,7 @@ def test_cannot_overwrite_cassette_raise_error_disabled(get_client, tmpdir):
 
 
 @pytest.mark.gen_test
-@vcr.use_cassette
+@vcr.use_cassette(path_transformer=vcr.default_vcr.ensure_suffix('.yaml'))
 def test_tornado_with_decorator_use_cassette(get_client):
     response = yield get_client().fetch(
         http.HTTPRequest('http://www.google.com/', method='GET')
diff --git a/vcr/config.py b/vcr/config.py
index 09fbdd6..a47938e 100644
--- a/vcr/config.py
+++ b/vcr/config.py
@@ -23,7 +23,7 @@ class VCR(object):
             return path
         return ensure
 
-    def __init__(self, path_transformer=None, before_record_request=None,
+    def __init__(self, path_transformer=lambda x: x, before_record_request=None,
                  custom_patches=(), filter_query_parameters=(), ignore_hosts=(),
                  record_mode="once", ignore_localhost=False, filter_headers=(),
                  before_record_response=None, filter_post_data_parameters=(),
@@ -59,7 +59,7 @@ class VCR(object):
         self.ignore_hosts = ignore_hosts
         self.ignore_localhost = ignore_localhost
         self.inject_cassette = inject_cassette
-        self.path_transformer = path_transformer or self.ensure_suffix('.yaml')
+        self.path_transformer = path_transformer
         self.func_path_generator = func_path_generator
         self._custom_patches = tuple(custom_patches)