diff --git a/requests/models.py b/requests/models.py
index 11434ef4..74385674 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -870,4 +870,6 @@ class Response(object):
         if not self._content_consumed:
             self.raw.close()
 
-        return self.raw.release_conn()
+        release_conn = getattr(self.raw, 'release_conn', None)
+        if release_conn is not None:
+            release_conn()
diff --git a/tests/test_requests.py b/tests/test_requests.py
index dcf14eec..6292f9d7 100755
--- a/tests/test_requests.py
+++ b/tests/test_requests.py
@@ -1393,6 +1393,15 @@ class TestRequests:
         with pytest.raises(ValueError):
             r.json()
 
+    def test_response_without_release_conn(self):
+        """Test `close` call for non-urllib3-like raw objects.
+        Should work when `release_conn` attr doesn't exist on `response.raw`.
+        """
+        resp = requests.Response()
+        resp.raw = StringIO.StringIO('test')
+        assert not resp.raw.closed
+        resp.close()
+        assert resp.raw.closed
 
 class TestCaseInsensitiveDict: