diff --git a/devops-service/lib/executors/server_executor.rb b/devops-service/lib/executors/server_executor.rb
index 4aa63d3..2edf407 100644
--- a/devops-service/lib/executors/server_executor.rb
+++ b/devops-service/lib/executors/server_executor.rb
@@ -446,11 +446,16 @@ module Devops
       end
 
       def compute_run_list
-        rlist = Set.new.merge(@deploy_env.provider_instance.run_list).merge(@project.run_list).merge(@deploy_env.run_list).merge(@server.run_list)
+        rlist = []
+        [@deploy_env.provider_instance.run_list, @project.run_list, @deploy_env.run_list, @server.run_list].each do |sub_run_list|
+          rlist += sub_run_list if sub_run_list.is_a?(Array)
+        end
+        rlist = Set.new(rlist)
         if @server.stack
           stack = Devops::Db.connector.stack(@server.stack)
           out << "Stack run list: #{stack.run_list.join(", ")}\n"
-          rlist.merge(stack.run_list)
+          srl = stack.run_list
+          rlist.merge(srl) if srl.is_a?(Array)
         end
         rlist.to_a
       end