diff --git a/.github/workflows/master_merge.yml b/.github/workflows/master_merge.yml
index 9d581c6..9f9fb2a 100644
--- a/.github/workflows/master_merge.yml
+++ b/.github/workflows/master_merge.yml
@@ -9,7 +9,7 @@ env:
 
 jobs:
   build-ckan-2-9:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2