diff --git a/monai/engines/evaluator.py b/monai/engines/evaluator.py
index b329462e24..e3e70d8b32 100644
--- a/monai/engines/evaluator.py
+++ b/monai/engines/evaluator.py
@@ -114,7 +114,7 @@ def __init__(
             event_to_attr=event_to_attr,
             decollate=decollate,
         )
-        self.mode = look_up_option(mode, ForwardMode)
+        mode = look_up_option(mode, ForwardMode)
         if mode == ForwardMode.EVAL:
             self.mode = eval_mode
         elif mode == ForwardMode.TRAIN:
diff --git a/tests/test_prepare_batch_default.py b/tests/test_prepare_batch_default.py
index 5417c8ca51..96051b5e82 100644
--- a/tests/test_prepare_batch_default.py
+++ b/tests/test_prepare_batch_default.py
@@ -43,6 +43,7 @@ def test_content(self):
             non_blocking=False,
             prepare_batch=PrepareBatchDefault(),
             decollate=False,
+            mode="eval",
         )
         evaluator.run()
         output = evaluator.state.output