diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index fd256fd75b62a293ee277bdd40b841be9c75000b..f7c7f417b315384437729975c7120d4c92df92d1 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -170,6 +170,9 @@ build-spack-env-on-runner:
     - cp packages.yaml $SPACK_DEV_PATH/etc/spack/packages.yaml
     # SPACK PATCH: see https://github.com/spack/spack/pull/35290
     - sed -i 's/solver.solve(abstract_specs)/solver.solve(abstract_specs, tests=kwargs.get("tests", False))/g' $SPACK_DEV_PATH/lib/spack/spack/concretize.py
+    # the post-build logs on install-time-test-logs.txt gets ovewritten by the post-install logs.
+    # quick fix for that: (TODO: investigate more and open PR)
+    - sed -i "s/self.file_like, 'w'/self.file_like, 'a'/g" $SPACK_DEV_PATH/lib/spack/llnl/util/tty/log.py
     - |
       cat <<EOF > $SPACK_DEV_PATH/etc/spack/defaults/upstreams.yaml
       upstreams:
@@ -235,6 +238,9 @@ sync-gitlab-spack-instance:
       fi
     # SPACK PATCH: see https://github.com/spack/spack/pull/35290
     - sed -i 's/solver.solve(abstract_specs)/solver.solve(abstract_specs, tests=kwargs.get("tests", False))/g' $SPACK_PATH/lib/spack/spack/concretize.py
+    # the post-build logs on install-time-test-logs.txt gets ovewritten by the post-install logs.
+    # quick fix for that: (TODO: investigate more and open PR)
+    - sed -i "s/self.file_like, 'w'/self.file_like, 'a'/g" $SPACK_PATH/lib/spack/llnl/util/tty/log.py
     - cp $CI_PROJECT_DIR/packages.yaml $SPACK_PATH/etc/spack/packages.yaml
     - . $SPACK_PATH/share/spack/setup-env.sh
     # - spack bootstrap untrust github-actions