diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index a0da246..4798f93 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -4,7 +4,7 @@ on:
   pull_request:
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       - uses: XAMPPRocky/deploy-mdbook@v1.1