diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index df314f9..5e5046b 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -19,8 +19,8 @@ jobs:
         config:
           - {os: windows-latest,  r: 'release'}
           - {os: macOS-latest,    r: 'release'}
-          ##- {os: ubuntu-20.04,    r: 'release'}
-          ##- {os: ubuntu-latest,   r: 'devel'}
+          - {os: ubuntu-20.04,    r: 'release', rspm: 'https://packagemanager.rstudio.com/cran/__linux__/focal/latest'}
+          - {os: ubuntu-20.04,    r: 'devel',   rspm: 'https://packagemanager.rstudio.com/cran/__linux__/focal/latest'}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}