diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index c561bf6..65f62f7 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -12,6 +12,7 @@ jobs:
       && contains('schedule workflow_dispatch', github.event_name)
     strategy:
       fail-fast: false
+      max-parallel: 1
       matrix:
         pkg: [asli, bap-asli-plugin, bap-uq-pac, basil]
     uses: ./.github/workflows/nix.yml
diff --git a/.github/workflows/nix.yml b/.github/workflows/nix.yml
index ea4af6f..3c7870d 100644
--- a/.github/workflows/nix.yml
+++ b/.github/workflows/nix.yml
@@ -14,11 +14,9 @@ jobs:
 
     - run: nix-build ./update-shell.nix
     - run: |
-        nix-shell ./update-shell.nix --pure --keep NIX_PATH \
-          --run './update.py check -A ${{inputs.pkg}}'
+        nix-shell ./update-shell.nix --run './update.py check -A ${{inputs.pkg}}'
 
   do-upgrade:
-    concurrency: do-upgrade  # one package upgrade in-flight at a time
     runs-on: ubuntu-latest
     needs: check
     steps:
@@ -33,8 +31,7 @@ jobs:
         git config user.name 'github-actions[bot]'
         git config user.email 41898282+github-actions[bot]@users.noreply.github.com
     - run: |
-        nix-shell ./update-shell.nix --pure --keep NIX_PATH \
-          --run './update.py do-upgrade -A ${{inputs.pkg}}'
+        nix-shell ./update-shell.nix --run './update.py do-upgrade -A ${{inputs.pkg}}'
     - run: git push
 
   build: