diff --git a/.github/workflows/haskell-ci.yaml b/.github/workflows/haskell-ci.yaml
index 4bdf64b..f3db2c9 100644
--- a/.github/workflows/haskell-ci.yaml
+++ b/.github/workflows/haskell-ci.yaml
@@ -106,12 +106,13 @@ jobs:
         apt-get update -y
         apt-get install -y autoconf build-essential zlib1g-dev libgmp-dev curl libncurses5 libtinfo5 libncurses5-dev libtinfo-dev
 
-        curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE=1 BOOTSTRAP_HASKELL_MINIMAL=1 sh
+        curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE=1 BOOTSTRAP_HASKELL_MINIMAL=1 BOOTSTRAP_HASKELL_INSTALL_NO_STACK=1 sh
 
         source ~/.ghcup/env
         ghcup install ghc --set ${{ matrix.ghc }}
         ghcup install cabal latest
 
+    # This version must stay old enough to remain compatible with the container image.
     - uses: actions/checkout@v1
 
     - name: Cabal version