diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3b1419c..02e0697 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -42,7 +42,8 @@ jobs:
       run: bundle exec rake compile test
       timeout-minutes: 5
 
-  test2:
+  build-ibm:
+    if: github.repository == 'ruby/zlib'
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false