Birth in Belgium/Citizenship

I was astonished to learn that my newborn was given Belgian citizenship by default by the local authorities as I have lived here for x number of years even though I am not Belgian and neither is my partner. I do not have anything against Belgium per se, but I want my child to be a national of either the country that I am from or of my partner's. I am under the impression that 'jus sanguinis' applies here as opposed to 'jus soli', but I suppose that this is not the case. Has anyone else experienced something similar and can tell me what they did? Thank you.