~そうにないです versus ~なさそうです

[healer]

よしさんは心変わりをしそうにないです。
I saw the above at one of the language learning web site. Is it grammatical?
I had expected the following.
よしさんは心変わりをしなさそうです。
What could be the difference in usage? Is the latter grammatical too?

 

[Toritoribe]

Both are correct. The latter sounds more colloquial.