diff --git a/tests/integration/test_proxy.py b/tests/integration/test_proxy.py
index 3212b24..ce67e60 100644
--- a/tests/integration/test_proxy.py
+++ b/tests/integration/test_proxy.py
@@ -37,6 +37,6 @@ def proxy_server(httpbin):
 
 def test_use_proxy(tmpdir, httpbin, proxy_server):
     '''Ensure that it works with a proxy.'''
-    with vcr.use_cassette(str(tmpdir.join('proxy.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join('proxy.yaml'))):
         requests.get(httpbin.url, proxies={'http': proxy_server})
         requests.get(httpbin.url, proxies={'http': proxy_server})
diff --git a/vcr/stubs/__init__.py b/vcr/stubs/__init__.py
index 6ebe2e8..763204e 100644
--- a/vcr/stubs/__init__.py
+++ b/vcr/stubs/__init__.py
@@ -136,7 +136,7 @@ class VCRConnection(object):
 
     def _uri(self, url):
         """Returns request absolute URI"""
-        if not url.startswith('/'):
+        if url and not url.startswith('/'):
             # Then this must be a proxy request.
             return url
         uri = "{0}://{1}{2}{3}".format(