diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 20578b7..a5ad304 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -11,7 +11,7 @@ on:
 
 jobs:
   shellcheck:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     if: github.repository_owner == 'hwdsl2' && github.event_name == 'push'
     steps:
       - uses: actions/checkout@v2
@@ -37,7 +37,7 @@ jobs:
           shellcheck **/*.sh
 
   test_set_1:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     if: github.repository_owner == 'hwdsl2'
     strategy:
       matrix:
@@ -245,7 +245,7 @@ jobs:
           docker rmi "${OS_VERSION//:}-test" || true
 
   test_set_2:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     if: github.repository_owner == 'hwdsl2'
     strategy:
       matrix: