Error during installation

Gauche error message

gcc -g -O2 -Wall -Wextra -Wno-unused-label -no-cpp-precomp -fPIC -fno-common    -bundle -flat_namespace -undefined suppress -o rfc--tls--mbed.so tls-mbed.o -L"../../src"  \

"../../src/gosh" -ftest "../../ext/xlink" -l -g "rfc" \
          -b "../.." -s . rfc--mime.so rfc--822.so mime.sci 822.sci
link /Users/takashi/.scheme-env/work/gauche/0.9.8/build-20190709_162252.dyMWDDMC/Gauche-0.9.8/ext/rfc/rfc--mime.so <- ../../src/rfc--mime.so
link /Users/takashi/.scheme-env/work/gauche/0.9.8/build-20190709_162252.dyMWDDMC/Gauche-0.9.8/ext/rfc/rfc--822.so <- ../../src/rfc--822.so
link /Users/takashi/.scheme-env/work/gauche/0.9.8/build-20190709_162252.dyMWDDMC/Gauche-0.9.8/ext/rfc/mime.sci <- ../../lib/rfc/mime.sci
link /Users/takashi/.scheme-env/work/gauche/0.9.8/build-20190709_162252.dyMWDDMC/Gauche-0.9.8/ext/rfc/822.sci <- ../../lib/rfc/822.sci
*** ERROR: string required, but got #f
Stack Trace:
_______________________________________
  0  (rxmatch #/[\-._]/ ver)
        at "../../lib/gauche/version.scm":108
  1  (next-component a-ver)
        at "../../lib/gauche/version.scm":129
  2  (version-compare a b)
        at "../../lib/gauche/version.scm":141
  3  (version>=? openssl-version "1.1")
        at "././ssltest-mod.scm":66
make[2]: *** [axTLS/ssl/test/ssltest.mod.c] Error 70
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [tls] Error 2
make: *** [all] Error 1

$ uname -a
Darwin *** 18.6.0 Darwin Kernel Version 18.6.0: Thu Apr 25 23:16:27 PDT 2019; root:xnu-4903.261.4~2/RELEASE_X86_64 x86_64