Change header/footer font with groff mm

I am currently testing the mm and mom macro packages and noticed that the default font family is not used for headers/footers with mm (unlike mom, which uses the selected font for all text). My test file contains the following:

.nr L 29.7c
.nr W 16c
.nr O 2.5c
.nr N 1
.so /opt/homebrew/Cellar/groff/1.23.0/share/groff/1.23.0/tmac/m.tmac

.fam Garamond
.ds HF 3 3 3
.ds HP +4 +2 0
.S 12

but the header (and footer) content is still set in Times New Roman. I tried putting the fam request first, to no effect. The mm manual provides some information on header/footer content in chapter 9, but does not mention selecting/changing the font.