diff --git a/.github/workflows/build_book.yml b/.github/workflows/build_book.yml
index 2e4a3ddb..b74774f9 100644
--- a/.github/workflows/build_book.yml
+++ b/.github/workflows/build_book.yml
@@ -34,7 +34,7 @@ jobs:
         run: make
 
   pdfhtml:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22-04
 
     steps:
       - uses: actions/checkout@v4