diff --git a/.ci/bootstrap_spack.sh b/.ci/bootstrap_spack.sh
index a8e79ff14cec0ddd24db5ee67c56c94af424630d..efe45e6729f807ee5acbb74f20e4cbbb2175009a 100755
--- a/.ci/bootstrap_spack.sh
+++ b/.ci/bootstrap_spack.sh
@@ -26,7 +26,7 @@ ccache -s
 sed -i '/ccache:/c\  ccache: true' "${MY_SPACK_FOLDER}/etc/spack/defaults/config.yaml"
 
 # build with all available processes
-sed -i "/build_jobs:/c\  build_jobs: $(nproc)" "${MY_SPACK_FOLDER}/etc/spack/defaults/config.yaml"
+sed -i "/# build_jobs:/c\  build_jobs: $(nproc)" "${MY_SPACK_FOLDER}/etc/spack/defaults/config.yaml"
 
 # add system compiler
 ${MY_SPACK_BIN} compiler add --scope site /usr/bin