diff --git a/.github/workflows/flowzone.yml b/.github/workflows/flowzone.yml
index 0b42f9ab..6e579653 100644
--- a/.github/workflows/flowzone.yml
+++ b/.github/workflows/flowzone.yml
@@ -20,5 +20,5 @@ jobs:
       (github.event.pull_request.head.repo.full_name != github.repository && github.event_name == 'pull_request_target')
     secrets: inherit
     with:
-      tests_run_on: '["ubuntu-latest","macos-latest","windows-2019"]'
+      tests_run_on: '["ubuntu-18.04","macos-latest","windows-2019"]'
       restrict_custom_actions: false