How to load partial optimizer checkpoint

Hi,

I am trying fine-tune a model with an additional module compared to the pre-trained model (similar to this post). Loading the model state dict works fine using the strict=False option. However, for the optimizer I get the following error:

ValueError: loaded state dict contains a parameter group that doesn't match the size of optimizer's group

How do I load a state from an optimizer for which the new model has an additional module?

Thanks!