diff --git a/Docker/shellb3-cspp-py38.Dockerfile b/Docker/shellb3-cspp-py38.Dockerfile
index c1451bf6b4703579bcf9d68e2fea7b59dbb7ed82..e77a7df00f5e192f9dcd4866528d969f378ab3cd 100644
--- a/Docker/shellb3-cspp-py38.Dockerfile
+++ b/Docker/shellb3-cspp-py38.Dockerfile
@@ -16,7 +16,7 @@ WORKDIR /opt/shellb3-cspp-py38/ShellB3
 ENV MAKEFLAGS=-j24
 RUN ./shallbethree.sh mk_gcc8
 ARG LINUXCPUFLAGS="-march=ivybridge -fPIC"
-ENV LINUXCPUFLAGS
+ENV LINUXCPUFLAGS="${LINUXCPUFLAGS}"
 RUN ./shallbethree.sh mk_${TRIM}
 WORKDIR /work
 RUN echo export HOSTNAME=$(perl -ne '/.*"HOSTNAME": "(\w+)",/ && print "$1";' </opt/shellb3-cspp-py38/ShellB3/build/.build_env.json) >/etc/profile.d/99-build-host.sh