diff --git a/examples/deepvoice3/data.py b/examples/deepvoice3/data.py
index 0d0aaeb7f4cf9731df98e9540dd9512b93671f1a..46381744d9cf1899bd93901b3226dc859ec54ee8 100644
--- a/examples/deepvoice3/data.py
+++ b/examples/deepvoice3/data.py
@@ -189,11 +189,14 @@ class DataCollector(object):
         # text positions
         text_mask = (np.arange(1, 1 + max_text_length) <= np.expand_dims(
             text_lengths, -1)).astype(np.int64)
-        text_positions = np.arange(1, 1 + max_text_length) * text_mask
+        text_positions = np.arange(
+            1, 1 + max_text_length, dtype=np.int64) * text_mask
 
         # decoder_positions
         decoder_positions = np.tile(
-            np.expand_dims(np.arange(1, 1 + max_decoder_length), 0),
+            np.expand_dims(
+                np.arange(
+                    1, 1 + max_decoder_length, dtype=np.int64), 0),
             (batch_size, 1))
 
         return (text_sequences, text_lengths, text_positions, mel_specs,