diff --git a/onnxslim/third_party/onnx_graphsurgeon/exporters/onnx_exporter.py b/onnxslim/third_party/onnx_graphsurgeon/exporters/onnx_exporter.py
index f1c9999..47f350d 100644
--- a/onnxslim/third_party/onnx_graphsurgeon/exporters/onnx_exporter.py
+++ b/onnxslim/third_party/onnx_graphsurgeon/exporters/onnx_exporter.py
@@ -367,7 +367,8 @@ def export_onnx(graph: Graph, do_type_check=True, **kwargs) -> "onnx.ModelProto"
         kwargs["ir_version"] = graph.ir_version
 
     model = onnx.helper.make_model(onnx_graph, **kwargs)
-    model.metadata_props.extend(graph.metadata_props)
+    if graph.metadata_props is not None:
+        model.metadata_props.extend(graph.metadata_props)
     model.producer_name = graph.producer_name
     model.producer_version = graph.producer_version
     return model