diff --git a/.github/workflows/phpunit.yml b/.github/workflows/phpunit.yml
index b8411259b..7d91d2250 100644
--- a/.github/workflows/phpunit.yml
+++ b/.github/workflows/phpunit.yml
@@ -13,7 +13,7 @@ env:
 
 jobs:
   integration:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
 
     strategy:
       fail-fast: false