Latin composition question from D'Ooge

I’m studying Latin on my own, currently working through the new reprint of Latin for Beginners by D’Ooge, and am finding the key to the exercises available on Textkit extremely helpful. I really appreciate having it available.

But I have encountered a Latin composition phrase whose answer on Textkit I don’t understand:
pg. 125, “He is a beautiful animal and has great strength.”
The Textkit answer is: “Pulchrum est animal et vīs habet magna.”
Shouldn’t that be “Pulchrum est animal et vim habet magnam.”?
Or is there some reason for “vīs magna” to be in the nominative that I don’t understand?

It should be vim habet magnam as you said. Erare humanum est! :smiley: