diff --git a/onnxconv.py b/onnxconv.py
index 44fec91..584bb4e 100644
--- a/onnxconv.py
+++ b/onnxconv.py
@@ -150,7 +150,7 @@ def export_to_onnx(model, x_current, x_reference, file_name):
             (x_current, x_reference),
             file_name,
             export_params=True,
-            opset_version=19,
+            opset_version=15,
             do_constant_folding=True,
             input_names=['x_current', 'x_reference'],
             output_names=['f_r', 't_r', 't_c'],