diff --git a/paddlespeech/t2s/modules/nets_utils.py b/paddlespeech/t2s/modules/nets_utils.py
index 0a66a1c88..755190200 100644
--- a/paddlespeech/t2s/modules/nets_utils.py
+++ b/paddlespeech/t2s/modules/nets_utils.py
@@ -181,11 +181,11 @@ def make_pad_mask(lengths, xs=None, length_dim=-1):
     if length_dim == 0:
         raise ValueError("length_dim cannot be 0: {}".format(length_dim))
 
-    # check if ilens is 0-dim tensor, if so, add a dimension
     if lengths.ndim == 0:
-        lengths = lengths.unsqueeze(0)
+        bs = paddle.shape(lengths)
+    else:
+        bs = paddle.shape(lengths)
 
-    bs = paddle.shape(lengths)
     if xs is None:
         maxlen = paddle.cast(lengths.max(), dtype=bs.dtype)
     else: