diff --git a/pufferlib/sweep.py b/pufferlib/sweep.py
index 1212d8e1ec..9e237778c2 100644
--- a/pufferlib/sweep.py
+++ b/pufferlib/sweep.py
@@ -951,7 +951,7 @@ def early_stop(self, logs, target_key):
                 logs['is_loss_nan'] = True
                 return True
 
-        if 'uptime' not in logs or target_key not in logs:
+        if 'uptime' not in logs or target_key not in logs['env']:
             return False
 
         metric_val, cost = logs['env'][target_key], logs['uptime']