Fatal error: Unable to find local grunt. With Gruntfile.js

Question

(beginner post)(OS : mac)

I just install grunt on my local, and edit my "Gruntfile.js" in my project and when I try this :

grunt -v

It return :

Fatal error: Unable to find local grunt.

I'm well in my project and no problem for install using this :

npm install -g grunt-cli

I miss something ?

Thk for time.