diff --git a/tools/internal_ci/linux/grpc_build_protobuf_at_head.cfg b/tools/internal_ci/linux/grpc_build_protobuf_at_head.cfg
index 75f0dae2c79..fdb8192f3ad 100644
--- a/tools/internal_ci/linux/grpc_build_protobuf_at_head.cfg
+++ b/tools/internal_ci/linux/grpc_build_protobuf_at_head.cfg
@@ -29,3 +29,8 @@ env_vars {
   key: "RUN_TESTS_FLAGS"
   value: "protobuf"
 }
+
+env_vars {
+  key: "BAZEL_FLAGS"
+  value: "main"
+}