diff --git a/paddlespeech/s2t/exps/u2/model.py b/paddlespeech/s2t/exps/u2/model.py
index bdda0fd8c..09d0982ec 100644
--- a/paddlespeech/s2t/exps/u2/model.py
+++ b/paddlespeech/s2t/exps/u2/model.py
@@ -519,6 +519,7 @@ class U2Tester(U2Trainer):
             infer_model.ctc_activation, input_spec=input_spec)
 
         ######################### infer_model.forward_attention_decoder ########################
+        reverse_weight = 0.3
         input_spec = [
             # hyps, (B, U)
             paddle.static.InputSpec(shape=[None, None], dtype='int64'),
@@ -526,7 +527,8 @@ class U2Tester(U2Trainer):
             paddle.static.InputSpec(shape=[None], dtype='int64'),
             # encoder_out, (B,T,D)
             paddle.static.InputSpec(
-                shape=[batch_size, None, model_size], dtype='float32')
+                shape=[batch_size, None, model_size], dtype='float32'),
+            reverse_weight
         ]
         infer_model.forward_attention_decoder = paddle.jit.to_static(
             infer_model.forward_attention_decoder, input_spec=input_spec)
diff --git a/paddlespeech/s2t/models/u2/u2.py b/paddlespeech/s2t/models/u2/u2.py
index 632e0a615..e1e9b05d7 100644
--- a/paddlespeech/s2t/models/u2/u2.py
+++ b/paddlespeech/s2t/models/u2/u2.py
@@ -716,7 +716,7 @@ class U2BaseModel(ASRInterface, nn.Layer):
             hyps: paddle.Tensor,
             hyps_lens: paddle.Tensor,
             encoder_out: paddle.Tensor,
-            reverse_weight: float=0.0, ) -> paddle.Tensor:
+            reverse_weight: float=0.0) -> paddle.Tensor:
         """ Export interface for c++ call, forward decoder with multiple
             hypothesis from ctc prefix beam search and one encoder output
         Args: