diff --git a/.github/workflows/sandpaper-main.yaml b/.github/workflows/sandpaper-main.yaml
index e17707acd..9cd9f0ce9 100644
--- a/.github/workflows/sandpaper-main.yaml
+++ b/.github/workflows/sandpaper-main.yaml
@@ -21,7 +21,9 @@ on:
 jobs:
   full-build:
     name: "Build Full Site"
-    runs-on: ubuntu-latest
+    # 20245-01-01: ubuntu-latest is now 24.04 and R is not installed by default in the runner image
+    # pin to 22.04 for now. See: https://github.com/carpentries/sandpaper/issues/605
+    runs-on: ubuntu-22.04
     permissions:
       checks: write
       contents: write