diff --git a/.ci/apt-get-and-cache.sh b/.ci/apt-get-and-cache.sh
deleted file mode 100755
index be41da9d1528dac9aeeadca1dd13458e58c2cf84..0000000000000000000000000000000000000000
--- a/.ci/apt-get-and-cache.sh
+++ /dev/null
@@ -1,30 +0,0 @@
-#!/bin/bash
-
-# "apt update ; apt install", with caching of the downloaded packages
-# and current state, to minimise load on debian mirrors without having
-# to build a new docker image
-
-CACHE=.ci/debian-cache.tar.gz
-
-if [ -z "$1" ]; then
-    printf 'Usage: %s <package>...\n' "$0"
-    exit 1
-fi
-
-if ls -sh $CACHE; then
-    sudo tar xvaf $CACHE -C /var
-else
-    printf 'No debian cache to extract\n'
-fi
-
-# Remove the configuration that disable apt cache
-sudo rm /etc/apt/apt.conf.d/docker-clean
-
-sudo apt update -y -q
-# first only download the packages, so that they end up in the cache
-sudo DEBIAN_FRONTEND=noninteractive apt install -yqd "$@"
-sudo tar caf $CACHE -C /var lib/apt cache/apt
-ls -sh $CACHE
-
-# now really install the packages
-sudo DEBIAN_FRONTEND=noninteractive apt install -yq --no-download "$@"
diff --git a/.ci/apt-get.sh b/.ci/apt-get.sh
new file mode 100755
index 0000000000000000000000000000000000000000..79d9b4ad040013178923bc73bc8c5f92f31f4ac3
--- /dev/null
+++ b/.ci/apt-get.sh
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# "apt update ; apt install", but from the local mirror
+
+sudo cp .ci/sources.list /etc/apt/sources.list
+sudo apt update -yq
+sudo DEBIAN_FRONTEND=noninteractive apt install -yq --no-install-recommends "$@"
diff --git a/.ci/sources.list b/.ci/sources.list
new file mode 100644
index 0000000000000000000000000000000000000000..34836ad8be2e5a067df74df6fd8b0a03fe5606f0
--- /dev/null
+++ b/.ci/sources.list
@@ -0,0 +1,2 @@
+deb http://debian.polytech-lille.fr/debian buster main
+deb http://debian.polytech-lille.fr/debian buster-updates main
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b7669ba432c4cb3d92665a4412d61b607991803f..d0fce1b2ea0ac0189be6142a99d9c1679a7cd897 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -3,16 +3,13 @@ image: "coqorg/coq:latest"
 build:
   stage: build
   script:
-    - .ci/apt-get-and-cache.sh ghc cabal-install libghc-language-c-dev libghc-wl-pprint-text-dev libghc-optparse-applicative-dev libghc-data-default-dev libghc-aeson-dev
+    - .ci/apt-get.sh ghc cabal-install libghc-language-c-dev libghc-wl-pprint-text-dev libghc-optparse-applicative-dev libghc-data-default-dev libghc-aeson-dev
     - cabal build
     - cp dist/build/digger/digger digger
-  cache:
-    paths:
-      - .ci/*-cache.tar.gz
-    when: 'always'
   artifacts:
     paths:
       - digger
+    expire_in: 1 hour
 
 test:
   stage: test