net/libarcus fails to install

[Torfinn Ingolfsen]

net/libarcus builds, but fails to install:
root at kg-core2# make install
===>  Installing for libArcus-4.7.1_2,1
===>  Checking if libArcus is already installed
===>   Registering installation for libArcus-4.7.1_2,1
pkg-static: Unable to access file
/usr/ports/net/libarcus/work/stage/usr/local/lib/python3.7/site-packages/Arcus.so:No
such file or directory
*** Error code 1

Stop.
make: stopped in /usr/ports/net/libarcus
the reason seems to be that it builds for Python 3.8 instead of python 3.7:
root at kg-core2# ll work/stage/usr/local/lib
total 100
drwxr-xr-x   6 root  wheel    512 Dec 27 14:06 ./
drwxr-xr-x  13 root  wheel    512 Dec 27 14:06 ../
drwxr-xr-x   3 root  wheel    512 Dec 27 14:06 X11/
drwxr-xr-x   3 root  wheel    512 Dec 27 14:06 cmake/
drwxr-xr-x   2 root  wheel    512 Dec 27 14:06 debug/
lrwxr-xr-x   1 root  wheel     13 Dec 27 14:06 libArcus.so@ -> libArcus.so.3
-rwxr-xr-x   1 root  wheel  75328 Dec 27 14:06 libArcus.so.1.1.0*
lrwxr-xr-x   1 root  wheel     17 Dec 27 14:06 libArcus.so.3@ ->
libArcus.so.1.1.0
drwxr-xr-x   3 root  wheel    512 Dec 27 14:06 python3.8/
root at kg-core2# ll work/stage/usr/local/lib/python3.8/site-packages/
total 68
drwxr-xr-x  2 root  wheel    512 Dec 27 14:06 ./
drwxr-xr-x  3 root  wheel    512 Dec 27 14:06 ../
-rwxr-xr-x  1 root  wheel  59608 Dec 27 14:06 Arcus.so*
I'm not sure why, since pyton37 is still default, according to
FreshPorts. Both pythons are installed here:
root at kg-core2# pkg info python3*
python37-3.7.9_1
python38-3.8.7

This on FreeBSD 11.4-release-p5:
root at kg-core2# uname -a
FreeBSD kg-core2.kg4.no 11.4-RELEASE-p5 FreeBSD 11.4-RELEASE-p5 #0:
Tue Dec  1 11:46:55 UTC 2020
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64

Any more info I can provide?
-- 
mvh
Torfinn