ENGINE-03052 The form key is not initialized

I was getting below error when i query using createNativeQuery() function,

return engine.getTaskService().createNativeTaskQuery().sql(WorkflowConstants.SQL_QUERY).listPage(firstResult,
        maxResults);
{
    "type": "JsonMappingException",
    "message": "ENGINE-03052 The form key is not initialized. You must call initializeFormKeys() on the task query before you can retrieve the form key. (through reference chain: java.util.ArrayList[0]->org.camunda.bpm.engine.impl.persistence.entity.TaskEntity[\"formKey\"])"
}

Try this:

	public List<Task> findTasksBypid(String processInstanceId) {
		return taskService.createTaskQuery().processInstanceId(processInstanceId).initializeFormKeys().list();
	}