diff --git a/.github/workflows/ci-linux.yml b/.github/workflows/ci-linux.yml
index 69fb61380..7992d2199 100644
--- a/.github/workflows/ci-linux.yml
+++ b/.github/workflows/ci-linux.yml
@@ -22,7 +22,7 @@ jobs:
   build:
     name: CI on Linux
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
 
     steps:
     - name: Check out repository
diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index a82ddfd01..43f1202fb 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -22,7 +22,7 @@ jobs:
       matrix:
         os:
           - macos-latest
-          - ubuntu-latest
+          - ubuntu-20.04
           - windows-latest
 
     steps: