diff --git a/.github/workflows/haskell-ci.yml b/.github/workflows/haskell-ci.yml
index f473fe1ffeb078f744c57bff74aef23a8596fc73..4bad5a4b15ec28e0663963f411ca88aa2ca84317 100644
--- a/.github/workflows/haskell-ci.yml
+++ b/.github/workflows/haskell-ci.yml
@@ -8,9 +8,9 @@
 #
 # For more information, see https://github.com/haskell-CI/haskell-ci
 #
-# version: 0.11.20210111
+# version: 0.11.20210221
 #
-# REGENDATA ("0.11.20210111",["github","--config=cabal.haskell-ci","cabal.project"])
+# REGENDATA ("0.11.20210221",["github","--config=cabal.haskell-ci","cabal.project"])
 #
 name: Haskell-CI
 on:
@@ -22,7 +22,7 @@ on:
       - master
 jobs:
   linux:
-    name: Haskell-CI Linux - GHC ${{ matrix.ghc }}
+    name: Haskell-CI - Linux - GHC ${{ matrix.ghc }}
     runs-on: ubuntu-18.04
     container:
       image: buildpack-deps:bionic
@@ -30,7 +30,9 @@ jobs:
     strategy:
       matrix:
         include:
-          - ghc: 8.10.3
+          - ghc: 9.0.1
+            allow-failure: false
+          - ghc: 8.10.4
             allow-failure: false
           - ghc: 8.8.4
             allow-failure: false
@@ -56,7 +58,7 @@ jobs:
           apt-get install -y --no-install-recommends gnupg ca-certificates dirmngr curl git software-properties-common
           apt-add-repository -y 'ppa:hvr/ghc'
           apt-get update
-          apt-get install -y ghc-$GHC_VERSION cabal-install-3.2
+          apt-get install -y ghc-$GHC_VERSION cabal-install-3.4
         env:
           GHC_VERSION: ${{ matrix.ghc }}
       - name: Set PATH and environment variables
@@ -69,12 +71,13 @@ jobs:
           echo "HC=$HC" >> $GITHUB_ENV
           echo "HCPKG=/opt/ghc/$GHC_VERSION/bin/ghc-pkg" >> $GITHUB_ENV
           echo "HADDOCK=/opt/ghc/$GHC_VERSION/bin/haddock" >> $GITHUB_ENV
-          echo "CABAL=/opt/cabal/3.2/bin/cabal -vnormal+nowrap" >> $GITHUB_ENV
+          echo "CABAL=/opt/cabal/3.4/bin/cabal -vnormal+nowrap" >> $GITHUB_ENV
           HCNUMVER=$(${HC} --numeric-version|perl -ne '/^(\d+)\.(\d+)\.(\d+)(\.(\d+))?$/; print(10000 * $1 + 100 * $2 + ($3 == 0 ? $5 != 1 : $3))')
           echo "HCNUMVER=$HCNUMVER" >> $GITHUB_ENV
           echo "ARG_TESTS=--enable-tests" >> $GITHUB_ENV
           if [ $((HCNUMVER >= 70800)) -ne 0 ] ; then echo "ARG_BENCH=--enable-benchmarks" >> $GITHUB_ENV ; else echo "ARG_BENCH=--disable-benchmarks" >> $GITHUB_ENV ; fi
-          echo "ARG_COMPILER=--ghc --with-compiler=/opt/ghc/$GHC_VERSION/bin/ghc" >> $GITHUB_ENV
+          echo "HEADHACKAGE=false" >> $GITHUB_ENV
+          echo "ARG_COMPILER=--ghc --with-compiler=$HC" >> $GITHUB_ENV
           echo "GHCJSARITH=0" >> $GITHUB_ENV
         env:
           GHC_VERSION: ${{ matrix.ghc }}
@@ -122,10 +125,15 @@ jobs:
         uses: actions/checkout@v2
         with:
           path: source
+      - name: initial cabal.project for sdist
+        run: |
+          touch cabal.project
+          echo "packages: $GITHUB_WORKSPACE/source/containers" >> cabal.project
+          echo "packages: $GITHUB_WORKSPACE/source/containers-tests" >> cabal.project
+          cat cabal.project
       - name: sdist
         run: |
           mkdir -p sdist
-          cd source || false
           $CABAL sdist all --output-dir $GITHUB_WORKSPACE/sdist
       - name: unpack
         run: |
diff --git a/containers-tests/containers-tests.cabal b/containers-tests/containers-tests.cabal
index cbdf8bbdfa65d345c59b9508da3550b819d05512..3e5ba681dc73966284b2349103e166596b16b6e9 100644
--- a/containers-tests/containers-tests.cabal
+++ b/containers-tests/containers-tests.cabal
@@ -26,7 +26,7 @@ extra-source-files:
   benchmarks/LookupGE/*.hs
 
 tested-with:
-  GHC ==7.6.3 || ==7.8.4 || ==7.10.3 || ==8.0.2 || ==8.2.2 || ==8.4.4 || ==8.6.5 || ==8.8.4 || ==8.10.3
+  GHC ==7.6.3 || ==7.8.4 || ==7.10.3 || ==8.0.2 || ==8.2.2 || ==8.4.4 || ==8.6.5 || ==8.8.4 || ==8.10.4 || ==9.0.1
 
 source-repository head
   type:     git
diff --git a/containers/containers.cabal b/containers/containers.cabal
index 1a33e0ed091421268bb8bbc0005ea12056068db7..eaa9020c1d2b331395aefbd6d5427fcbd0cfa12a 100644
--- a/containers/containers.cabal
+++ b/containers/containers.cabal
@@ -25,7 +25,7 @@ extra-source-files:
     include/containers.h
     changelog.md
 
-tested-with: GHC==8.10.3, GHC==8.8.4, GHC==8.6.5, GHC==8.4.4, GHC==8.2.2, GHC==8.0.2, GHC==7.10.3, GHC==7.8.4, GHC==7.6.3
+tested-with: GHC==9.0.1, GHC==8.10.4, GHC==8.8.4, GHC==8.6.5, GHC==8.4.4, GHC==8.2.2, GHC==8.0.2, GHC==7.10.3, GHC==7.8.4, GHC==7.6.3
 
 source-repository head
     type:     git