diff --git a/src/llamafactory/chat/hf_engine.py b/src/llamafactory/chat/hf_engine.py
index 260b1dc5..897017e0 100644
--- a/src/llamafactory/chat/hf_engine.py
+++ b/src/llamafactory/chat/hf_engine.py
@@ -178,9 +178,11 @@ class HuggingfaceEngine(BaseEngine):
 
         mm_inputs = template.mm_plugin.get_mm_inputs(**mm_input_dict, batch_ids=[prompt_ids], processor=processor)
         for key, value in mm_inputs.items():
-            if isinstance(value, list) and all(isinstance(v, torch.Tensor) for v in value):  # for pixtral inputs
+            if isinstance(value, list) and isinstance(value[0], torch.Tensor):  # for pixtral inputs
                 value = torch.stack(value)  # assume they have same sizes
-            elif isinstance(value, list) and all(isinstance(v, list) for v in value):  # for minicpmv inputs
+            elif (
+                isinstance(value, list) and isinstance(value[0], list) and isinstance(value[0][0], torch.Tensor)
+            ):  # for minicpmv inputs
                 value = torch.stack([torch.stack(v) for v in value])
             elif not isinstance(value, torch.Tensor):
                 value = torch.tensor(value)