Thanks for the feedback. I could reproduce the problem, it seems the micropython server that SquareLine Studio uses in the background, doesn’t like any fonts created with a name that begins with ‘montserrat’, no matter if there’s a space after it or not. Font named ‘Montserrat’ (with 1st letter capital) still worked so it seems micropython checks for ‘montserrat’ (all lower case) string to find built-in fonts. We’ll look for the cause. (The conclusion is the same for your other topic opened for this case: Add non default characters to the LV_FONT_MONTSERRAT_22 font )