diff --git a/data_juicer/ops/mapper/dialog_intent_detection_mapper.py b/data_juicer/ops/mapper/dialog_intent_detection_mapper.py
index 912fa8c3..5b283ad1 100644
--- a/data_juicer/ops/mapper/dialog_intent_detection_mapper.py
+++ b/data_juicer/ops/mapper/dialog_intent_detection_mapper.py
@@ -141,6 +141,8 @@ def build_input(self, history, query):
         if self.intent_candidates:
             input_prompt = self.candidate_template.format(
                 candidate_str=','.join(self.intent_candidates))
+        else:
+            input_prompt = ''
 
         if self.max_round > 0:
             input_prompt += ''.join(history[-self.max_round * 4:])
diff --git a/tests/ops/mapper/test_dialog_intent_detection_mapper copy.py b/tests/ops/mapper/test_dialog_intent_detection_mapper.py
similarity index 100%
rename from tests/ops/mapper/test_dialog_intent_detection_mapper copy.py
rename to tests/ops/mapper/test_dialog_intent_detection_mapper.py