diff --git a/package.json b/package.json
index ac542c3f9e866a44b7deb2176aed56e48051210d..f795dff9075e923d5cf7e93e79e812c440fdb393 100644
--- a/package.json
+++ b/package.json
@@ -38,7 +38,7 @@
     "update-host": "ts-node ./scripts/update-host.ts",
     "test": "scripty",
     "help": "scripty",
-    "postinstall": "cd client && yarn install",
+    "postinstall": "cd client && yarn install --pure-lockfile",
     "tsc": "tsc",
     "nodemon": "nodemon",
     "ts-node": "ts-node",
diff --git a/scripts/upgrade.sh b/scripts/upgrade.sh
index 748b0d947fde5ddcd41d4d3e6c273e8c96512106..ff6dce94f4d8d25a6648f6cb4a64bc0bf98bed4d 100755
--- a/scripts/upgrade.sh
+++ b/scripts/upgrade.sh
@@ -25,9 +25,7 @@ fi
 
 git pull origin $(git rev-parse --abbrev-ref HEAD) || exit -1
 
-yarn install
-yarn upgrade
-cd client && yarn upgrade && cd ../
+yarn install --pure-lockfile
 npm run build
 
 echo "\n\nUpgrade finished! You can restart PeerTube that may run the migration scripts."