Difference in font rendering in Emacs 28.1 and 28.2

I'm currently switching my package management from Debian to Guix, and so far it's been wonderful. However, I just found something very curious. In the screenshot, you can see my 'old' self compiled Emacs (28.1) and my new Emacs (28.2) installed via Guix. They render the same text in the same file, in the same theme, with the same font (as per M-x describe-font), but they look quite different. Here's a screenshot showing the two side by side: https://screenshots.200ok.ch/screenshot_2022_10_26-a7bdddc0.png The version to the left is quite thin, the weight seems off. However, the weight is the same. Changing the weight will not remove this discrepancy. Both Debian and Guix have the bold variant of Fira installed: https://screenshots.200ok.ch/screenshot_2022_10_26-36be0060.png Generally speaking, the bold variant works insofar that I can use it globally: https://screenshots.200ok.ch/screenshot_2022_10_26-5620acc4.png However, when used in a font-face, it won't become bold: https://screenshots.200ok.ch/screenshot_2022_10_26-bb7ddfd5.png I'm happy if anyone can point me to the necessary change to make the new install look the same as before. Thank you for your help! --- Update (8 days later): I've updated guix to current master (before I was on the latest stable version 1.3.0). It works now. I can't tell if it's the update to Emacs or the font, but I'm happy anyway^^

Are you referring to the headers not being bold or am I just too blind to see the difference?

Do you have bold variant of Fira installed on your old setup?

Both Debian and Guix have the bold variant of Fira installed: https://screenshots.200ok.ch/screenshot_2022_10_26-36be0060.png Generally speaking, the bold variant works insofar that I can use it globally: https://screenshots.200ok.ch/screenshot_2022_10_26-5620acc4.png However, when used in a font-face, it won't become bold: https://screenshots.200ok.ch/screenshot_2022_10_26-bb7ddfd5.png It's a good question. I'll add this info to the original post. Thank you!

Yes, the header isn't bold. I picked the spot as a representative. There's many spots where the two don't align, yet `M-x describe-face` say they use the same config.

There is a variable that shows you with which configure flags emacs has been compiled, maybe check for differences there