diff --git a/egs/wenetspeech/ASR/transducer_stateless/model.py b/egs/wenetspeech/ASR/transducer_stateless/model.py
index 3d562e1a8..016c58594 100644
--- a/egs/wenetspeech/ASR/transducer_stateless/model.py
+++ b/egs/wenetspeech/ASR/transducer_stateless/model.py
@@ -103,6 +103,15 @@ class Transducer(nn.Module):
         y_padded = y.pad(mode="constant", padding_value=0)
 
         y_padded = y_padded.to(torch.int64)
+
+        max_sym_id = torch.max(y_padded)
+        assert encoder_out.size(0) == decoder_out.size(0),\
+            [encoder_out.size(), decoder_out.size()]
+        assert encoder_out.size(2) == decoder_out.size(2),\
+            [encoder_out.size(), decoder_out.size()]
+        assert encoder_out.size(2) >= (max_sym_id + 1),\
+            [encoder_out.size(), max_sym_id]
+
         boundary = torch.zeros(
             (x.size(0), 4), dtype=torch.int64, device=x.device
         )