diff --git a/dpgen2/op/collect_data.py b/dpgen2/op/collect_data.py
index b1e057e5..68f397ff 100644
--- a/dpgen2/op/collect_data.py
+++ b/dpgen2/op/collect_data.py
@@ -95,9 +95,9 @@ def execute(
 
         ms = dpdata.MultiSystems(type_map=type_map)
         for ii in labeled_data:
-            if len(list(ii.rglob("fparam.npy"))) > 0:
+            if ii and len(list(ii.rglob("fparam.npy"))) > 0:
                 setup_ele_temp(False)
-            if len(list(ii.rglob("aparam.npy"))) > 0:
+            if ii and len(list(ii.rglob("aparam.npy"))) > 0:
                 setup_ele_temp(True)
             ss = dpdata.LabeledSystem(ii, fmt="deepmd/npy")
             ms.append(ss)