diff --git a/lib/capistrano/tasks/capistrano2.rb b/lib/capistrano/tasks/capistrano2.rb
index 6888f07..55861e2 100644
--- a/lib/capistrano/tasks/capistrano2.rb
+++ b/lib/capistrano/tasks/capistrano2.rb
@@ -59,8 +59,12 @@ def for_each_role
     end
 
     def run_as(cmd)
+      opts = {
+        roles: sidekiq_role
+      }
       su_user = fetch(:sidekiq_user)
-      run cmd, roles: sidekiq_role, shell: "su - #{su_user}"
+      opts[:shell] = "su - #{su_user}" if su_user
+      run cmd, opts
     end
 
     def quiet_process(pid_file, idx, sidekiq_role)