diff --git a/wpull/http/client.py b/wpull/http/client.py
index 7ad2aac8..d6e1244f 100644
--- a/wpull/http/client.py
+++ b/wpull/http/client.py
@@ -3,6 +3,7 @@
 import functools
 import gettext
 import logging
+import warnings
 
 from trollius import From, Return
 import trollius
@@ -157,7 +158,10 @@ def abort(self):
         self._session_complete = True
 
     def recycle(self):
-        assert self._session_complete
+        if not self._session_complete:
+            warnings.warn(_('HTTP session did not complete.'))
+
+            self.abort()
 
         if self._connection:
             self._connection_pool.check_in(self._connection)
diff --git a/wpull/http/client_test.py b/wpull/http/client_test.py
index add5e139..be495130 100644
--- a/wpull/http/client_test.py
+++ b/wpull/http/client_test.py
@@ -2,6 +2,7 @@
 import contextlib
 import functools
 import io
+import warnings
 
 from trollius import From
 
@@ -137,15 +138,19 @@ def test_client_recorder(self):
         self.assertIn(b'hello', recorder.response_data)
 
     @wpull.testing.async.async_test(timeout=DEFAULT_TIMEOUT)
-    def test_client_exception_close(self):
+    def test_client_did_not_complete(self):
         client = Client()
 
-        with self.assertRaises(AssertionError):
+        with warnings.catch_warnings(record=True) as warn_list:
+            warnings.simplefilter("always")
+
             with client.session() as session:
                 request = Request(self.get_url('/'))
                 response = yield From(session.fetch(request))
                 self.assertFalse(session.done())
 
+            self.assertEqual(1, len(warn_list))
+
         client = Client()
 
         with self.assertRaises(MyException):