diff --git a/.github/workflows/check.yaml b/.github/workflows/check.yaml
index 76070008..c82cce9f 100644
--- a/.github/workflows/check.yaml
+++ b/.github/workflows/check.yaml
@@ -34,6 +34,7 @@ jobs:
         with:
           r-version: ${{ matrix.config.r }}
           rtools-version: '43'
+          extra-repositories: 'https://mc-stan.org/r-packages/''
           http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true