Change listeners do not trigger when modifying Mixed attributes under the following circumstances:

• Boolean(true) to/from Int(1) 
• Boolean(false) to/from Int(0) 
• Date(10) to/from ObjectId(10) 

Mixed does type coercion and the same data might be represented by different types. This behavior might be misleading to the users, as they might not be only looking for data changes but also for type changes.