diff --git a/devops-service/lib/executors/stack_executor/stack_servers_persister.rb b/devops-service/lib/executors/stack_executor/stack_servers_persister.rb
index 4bbde06..dc98d9d 100644
--- a/devops-service/lib/executors/stack_executor/stack_servers_persister.rb
+++ b/devops-service/lib/executors/stack_executor/stack_servers_persister.rb
@@ -8,14 +8,7 @@ class Devops::Executor::StackExecutor
       @stack = stack
       @project = mongo.project(stack.project)
       @deploy_env = @project.deploy_env(stack.deploy_env)
-      @already_used_incrementers_values = mongo.stack_servers(stack.name).inject({}) do |hash, server|
-        next hash unless server.stack_info['incrementers_values']
-        server.stack_info['incrementers_values'].each do |name, value|
-          hash[name] ||= []
-          hash[name] << value
-        end
-        hash
-      end
+      @already_used_incrementers_values = get_already_used_incrementers_values
     end
 
     def persist(provider_info)
@@ -49,6 +42,18 @@ class Devops::Executor::StackExecutor
       user || 'ec2-user'
     end
 
+    def get_already_used_incrementers_values
+      mongo.stack_servers(stack.name).inject({}) do |hash, server|
+        incrementers_values = server.stack_info && server.stack_info['incrementers_values']
+        next hash unless incrementers_values
+        incrementers_values.each do |name, value|
+          hash[name] ||= []
+          hash[name] << value
+        end
+        hash
+      end
+    end
+
     def apply_name_builder(server_attrs, provider_info)
       name_builder = get_name_builder(provider_info)
       server_attrs['chef_node_name'] = name_builder.build_node_name