diff --git a/envs/monkey_zoo/blackbox/island_client/monkey_island_client.py b/envs/monkey_zoo/blackbox/island_client/monkey_island_client.py
index 28dc1f135..4f723e8a7 100644
--- a/envs/monkey_zoo/blackbox/island_client/monkey_island_client.py
+++ b/envs/monkey_zoo/blackbox/island_client/monkey_island_client.py
@@ -172,4 +172,4 @@ class MonkeyIslandClient(object):
 
     def is_all_monkeys_dead(self):
         agents = self.get_agents()
-        return all([a.stop_time is not None for a in agents])
+        return all((a.stop_time is not None for a in agents))