diff --git a/optimum/exporters/onnx/model_configs.py b/optimum/exporters/onnx/model_configs.py
index 10ddd5e7a0..8a4d1d6bc9 100644
--- a/optimum/exporters/onnx/model_configs.py
+++ b/optimum/exporters/onnx/model_configs.py
@@ -238,7 +238,7 @@ def inputs(self) -> Dict[str, Dict[int, str]]:
 
 
 class GPT2OnnxConfig(TextDecoderWithPositionIdsOnnxConfig):
-    DEFAULT_ONNX_OPSET = 13
+    DEFAULT_ONNX_OPSET = 14  # uses SDPA in Transformers, hence opset>=14.
     NORMALIZED_CONFIG_CLASS = NormalizedTextConfig.with_args(num_layers="n_layer", num_attention_heads="n_head")
 
 
@@ -260,7 +260,7 @@ class GPTNeoOnnxConfig(TextDecoderWithPositionIdsOnnxConfig):
 
 
 class GPTNeoXOnnxConfig(TextDecoderWithPositionIdsOnnxConfig):
-    DEFAULT_ONNX_OPSET = 13
+    DEFAULT_ONNX_OPSET = 14  # uses SDPA in Transformers, hence opset>=14.
     NORMALIZED_CONFIG_CLASS = NormalizedTextConfig