diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3074be5f..8e886a98 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,6 +26,7 @@ jobs:
         - windows-latest
         ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
         include:
+        - { os: windows-latest , ruby: mswin     } # ruby/ruby windows CI
         - { os: ubuntu-latest  , ruby: jruby-9.1 } # Ruby 2.3
         - { os: ubuntu-latest  , ruby: jruby-9.2 } # Ruby 2.5
         - { os: ubuntu-latest  , ruby: jruby-9.3 } # Ruby 2.7