Magick++ equivalent of "convert -background none" option

[vtagle-qsi]

Yet another SVG question I'm trying to figure out what the Magick++ equivalent is for convert's "-background none" option. Creating a black color with transparent alpha via this line:

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Magick::Color backgroundColor(0, 0, 0, QuantumRange); 

and calling backgroundColor() for the image with this color doesn't appear to have any effect. The full code looks like this:

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Magick::Image svgImage(filename);
Magick::Color backgroundColor(0, 0, 0, QuantumRange); 
svgImage.backgroundColor(backgroundColor); 
svgImage.magick("png");

Am I missing something here or doing steps in the wrong order? I tried figuring out what convert did but I couldn't see where it happened exactly.