Custom ontology import [potential bug]

Hello, I am using the Custom Ontology module and I have noticed a strange behaviour. When I create an ontology, I save its .ttl file.

If I edit that file (say, I add a property) and then import it, all the entities have an extra prefix added. For isntance:

boslit:myField (original file)
boslit:boslitmyField (what is imported by the module and what I see in my ‘vocabularies’ section).

Is this a bug or is it me mising something?

PS: what I do is then keeping a text file with the list of properties ready to copy and paste, I delete the previous vocabulary, and create a new one by copy-pasting my previous list with any edit I want.