diff --git a/example/speech_recognition/stt_io_bucketingiter.py b/example/speech_recognition/stt_io_bucketingiter.py
index 41b93f3bb9e5..c9e0b7d4a8bb 100644
--- a/example/speech_recognition/stt_io_bucketingiter.py
+++ b/example/speech_recognition/stt_io_bucketingiter.py
@@ -83,7 +83,7 @@ def __init__(self, count, datagen, batch_size, num_label, init_states, seq_lengt
             durations = durations
             audio_paths = audio_paths
             texts = texts
-        self.trainDataList = zip(durations, audio_paths, texts)
+        self.trainDataList = list(zip(durations, audio_paths, texts))
 
         self.trainDataIter = iter(self.trainDataList)
         self.is_first_epoch = True