diff --git a/tools/internal_ci/macos/pull_request/grpc_basictests_ruby.cfg b/tools/internal_ci/macos/pull_request/grpc_basictests_ruby.cfg
index 187e8fb83aa..d97f8968e0b 100644
--- a/tools/internal_ci/macos/pull_request/grpc_basictests_ruby.cfg
+++ b/tools/internal_ci/macos/pull_request/grpc_basictests_ruby.cfg
@@ -27,5 +27,5 @@ action {
 
 env_vars {
   key: "RUN_TESTS_FLAGS"
-  value: "-f basictests macos ruby obs 4 --max_time=3600"
+  value: "-f basictests macos ruby -j 1 --inner_jobs 4 --max_time=3600"
 }