diff --git a/onnxscript/function_libs/torch_lib/ops/nn.py b/onnxscript/function_libs/torch_lib/ops/nn.py
index d91a12ec35..8bb8bf0aa3 100644
--- a/onnxscript/function_libs/torch_lib/ops/nn.py
+++ b/onnxscript/function_libs/torch_lib/ops/nn.py
@@ -826,7 +826,7 @@ def aten_leaky_relu_backward(
 
 
 @torch_op("aten::linear", trace_only=True)
-def aten_linear(input: TFloat, weight: TFloat, bias: TFloat | None = None) -> TFloat:
+def aten_linear(input: TFloat, weight: TFloat, bias: Optional[TFloat] = None) -> TFloat:
     """linear(Tensor input, Tensor weight, Tensor? bias=None) -> Tensor"""
 
     if len(input.shape) == 2: