diff --git a/network.py b/network.py
index 082f322..f1f1859 100644
--- a/network.py
+++ b/network.py
@@ -295,7 +295,7 @@ class Network:
                 return [0]
             
         if tf_session == None:
-            with tf.Session():
+            with tf.Session() as session:
                 session.run(tf.global_variables_initializer())
                 self.restore_model(session)
                 outcomes = [ (method, do_eval(session,