diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 27037c388fedc154d2901e41979f44c84b701419..44739c1ec3d23664320092fcf129cb91926d800a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -19,7 +19,7 @@ validate-data:
    image: debian:buster
    script:
     - apt-get update && apt-get -y install ruby ruby-dev build-essential rake wget
-    - gem install bundler
+    - gem install bundler -v 1.17.3
     - bundle install
       # Add G5K CA certificate
     - wget --no-check-certificate -q https://www.grid5000.fr/certs/ca2019.grid5000.fr.crt -O /usr/local/share/ca-certificates/ca2019.grid5000.fr.crt
@@ -35,7 +35,7 @@ generate-reference-api:
    image: debian:buster
    script:
     - apt-get update && apt-get -y install ruby ruby-dev build-essential rake git
-    - gem install bundler
+    - gem install bundler -v 1.17.3
     - bundle install
     - export TZ=Europe/Paris
     - rake reference-api
diff --git a/README.md b/README.md
index 2f62800af11a662dbe4537ad9a397038564ca80a..c0117a7add77edb26f8af4aee38cb87ac594bb11 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ See also:
 We use bundler to manage dependencies.
 
 ```
-apt install bundler
+apt install bundler # or gem install bundler -v 1.17.3
 bundler install --standalone # this installs dependencies in the 'bundle' directory
 rake reference-api # or other commands
 ```