diff --git a/.github/workflows/check.yaml b/.github/workflows/check.yaml
index 86fa893f..b9d4dc90 100644
--- a/.github/workflows/check.yaml
+++ b/.github/workflows/check.yaml
@@ -15,7 +15,7 @@ jobs:
       matrix:
         config:
           - {os: macOS-latest, r: 'release'}
-          - {os: windows-latest, r: 'release', rtools: '43'}
+          - {os: windows-latest, r: 'release', rtools: '42'}
           - {os: ubuntu-latest, r: 'devel', http-user-agent: 'release'}
           - {os: ubuntu-latest, r: 'release'}
           - {os: ubuntu-latest, r: 'oldrel-1'}
@@ -33,7 +33,7 @@ jobs:
       - uses: r-lib/actions/setup-r@v2
         with:
           r-version: ${{ matrix.config.r }}
-          rtools-version: '43'
+          rtools-version: '42'
           extra-repositories: 'https://mc-stan.org/r-packages/'
           http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
@@ -42,6 +42,14 @@ jobs:
         with:
           extra-packages: any::rcmdcheck, local::.
           needs: check
+          
+      - name: Install CmdStan
+        shell: Rscript {0}
+        run: |
+          install.packages("cmdstanr", repos = c("https://mc-stan.org/r-packages/", getOption("repos")))
+          cmdstanr::check_cmdstan_toolchain(fix = TRUE)
+          cmdstanr::install_cmdstan()
+          writeLines("options(brms.backend = \"cmdstanr\")", "~/.Rprofile")
 
       - uses: r-lib/actions/check-r-package@v2
         with: