diff --git a/paddlespeech/t2s/modules/nets_utils.py b/paddlespeech/t2s/modules/nets_utils.py
index 755190200..e32be0706 100644
--- a/paddlespeech/t2s/modules/nets_utils.py
+++ b/paddlespeech/t2s/modules/nets_utils.py
@@ -182,7 +182,7 @@ def make_pad_mask(lengths, xs=None, length_dim=-1):
         raise ValueError("length_dim cannot be 0: {}".format(length_dim))
 
     if lengths.ndim == 0:
-        bs = paddle.shape(lengths)
+        bs = paddle.shape(lengths.unsqueeze(0))
     else:
         bs = paddle.shape(lengths)