Direction map rose not obeying font settins


I’m placing a large direction rose on a map. The relevant part of the code is this:

gmt coast -Df \
	-Wthinnest,darkgreen -Gdarkgreen -Bpxf5a10g10 -Bpyf5a10g10\
	-LjBR+w1000k+f+o0.7c+u -Tmg${cen}+w6c+t45/10/5+pthinner,180 \
	--MAP_DEFAULT_PEN=thinner,180 \
	--FONT_ANNOT_SECONDARY=10p,Helvetica,180 \
	--MAP_TICK_PEN_SECONDARY=thinner,180 \

But no matter what font size I choose for FONT_ANNOT_SECONDARY it is ignored and simply scales depending on the width of the direction rose.

Here is an example of what it looks like: