diff --git a/dpgen2/utils/download_dpgen2_artifacts.py b/dpgen2/utils/download_dpgen2_artifacts.py
index b5f69153..8ab4cb61 100644
--- a/dpgen2/utils/download_dpgen2_artifacts.py
+++ b/dpgen2/utils/download_dpgen2_artifacts.py
@@ -359,9 +359,9 @@ def _dl_step_item(
     [step_key, io, name] = item.split(global_step_def_split)
     pref = _item_path(prefix, item)
     if io in ["input"]:
-        target = step.inputs.artifacts[name]
+        target = step.inputs.artifacts.get(name)
     elif io in ["output"]:
-        target = step.outputs.artifacts[name]
+        target = step.outputs.artifacts.get(name)
     else:
         raise RuntimeError("unknown io style {io}")
     try:
diff --git a/tests/utils/test_dl_dpgen2_arti.py b/tests/utils/test_dl_dpgen2_arti.py
index c1166678..a9f251ac 100644
--- a/tests/utils/test_dl_dpgen2_arti.py
+++ b/tests/utils/test_dl_dpgen2_arti.py
@@ -28,6 +28,9 @@
 
 
 class MockedArti:
+    def get(self, key):
+        return self.__getitem__(key)
+
     def __getitem__(
         self,
         key,
diff --git a/tests/utils/test_dl_dpgen2_arti_by_def.py b/tests/utils/test_dl_dpgen2_arti_by_def.py
index 91d35e93..e6a30a32 100644
--- a/tests/utils/test_dl_dpgen2_arti_by_def.py
+++ b/tests/utils/test_dl_dpgen2_arti_by_def.py
@@ -30,6 +30,9 @@
 
 
 class MockedArti:
+    def get(self, key):
+        return self.__getitem__(key)
+
     def __getitem__(
         self,
         key,