Thumb blocking

Hi,

My name Olivier, a new and exited student.

I was wondering, while I was playing my major scale to practice my tongue blocking , I had difficulty not blowing in the next hole to the right of the one I was blowing in. For exemple, the blade of my tongue covered 1,2 and 3 while I was aiming in 4 but then the fifth was making sound too. So I had the Idea of blocking it with my right thumb which works like a charm. Would it be a bad habit if I kept using it ? I couldn't find anything about it on the web so that's why I'm asking.

Thanks, you will surely hear about me again in a near future.

Sincerely,

Olivier Savoie