There appears to be some problem with the dependency tracking. The workaround is to delete the build folder. There is some dependency code, but I can't seem to get it to work: https://github.com/SymbiFlow/sphinxcontrib-hdl-diagrams/blob/5166ade92cb855d87c34fd713b8f489e7dd04561/sphinxcontrib_hdl_diagrams/__init__.py#L204