Version

3.1.4

Reproduction link

https://codesandbox.io/s/mystifying-pine-2wx6c

Steps to reproduce

Click on the button and see the console. You will see that objects are unequal

What is expected?

Objects are equal. It works with vue 2 https://codesandbox.io/s/practical-margulis-2fgkq

What is actually happening?

Objects are unequal

You need to use toRaw, as described in docs, to get the original object reference