diff --git a/paddle/fluid/operators/sequence_ops/sequence_mask_op.h b/paddle/fluid/operators/sequence_ops/sequence_mask_op.h
index 18acb735cecabd1e01f7821c880fd8ed5e52971f..8fceed3558b4357b7863368c18add329ea9922b3 100644
--- a/paddle/fluid/operators/sequence_ops/sequence_mask_op.h
+++ b/paddle/fluid/operators/sequence_ops/sequence_mask_op.h
@@ -36,12 +36,10 @@ class SequenceMaskOp : public framework::OperatorWithKernel {
     PADDLE_ENFORCE(ctx->HasInput("X"), "Input(X) must exist");
     PADDLE_ENFORCE(ctx->HasOutput("Y"), "Output(Y) must exist");
 
-    auto maxlen = ctx->Attrs().Get<int>("maxlen");
-    if (maxlen > 0) {  // We can only infershape when maxlen > 0
-      auto dim = framework::vectorize2int(ctx->GetInputDim("X"));
-      dim.push_back(maxlen);
-      ctx->SetOutputDim("Y", framework::make_ddim(dim));
-    }
+    int maxlen = ctx->Attrs().Get<int>("maxlen");
+    auto dim = framework::vectorize2int(ctx->GetInputDim("X"));
+    dim.push_back(maxlen > 0 ? maxlen : -1);
+    ctx->SetOutputDim("Y", framework::make_ddim(dim));
   }
 };