diff --git a/.github/workflows/R-CMD-check.yaml b/.github/workflows/R-CMD-check.yaml
index e712a216..9fc3ff22 100644
--- a/.github/workflows/R-CMD-check.yaml
+++ b/.github/workflows/R-CMD-check.yaml
@@ -32,6 +32,7 @@ jobs:
 
           - {os: ubuntu-latest,  r: 'devel', http-user-agent: 'release'}
           - {os: ubuntu-latest,  r: 'release'}
+          - {os: ubuntu-latest,  r: 'release', locale: 'C'}
           - {os: ubuntu-latest,  r: 'oldrel-1'}
           - {os: ubuntu-latest,  r: 'oldrel-2'}
           - {os: ubuntu-latest,  r: 'oldrel-3'}
@@ -61,3 +62,5 @@ jobs:
         with:
           upload-snapshots: true
           build_args: 'c("--no-manual","--compact-vignettes=gs+qpdf")'
+        env:
+          LANG: ${{ matrix.config.locale || 'en_US.UTF8' }}