Error: "Glyph "DEFAULT" not in font" in Class DEFAULT in line: 1

Hi I’m having trouble with contextual alternatives, I found a tutorial at

I’m interested in the Cycling through glyph classes bit, I tried the sample code but get an error

Error: “Glyph “DEFAULT” not in font” in Class DEFAULT in line: 1
Error: “invalid token (text was “:”)” in Class DEFAULT in line: 1

I created 3 class names DEFAULT, ALT1 and ALT2

ALT1: A.ss01 B.ss01
ALT2: A.ss02 B.ss02

and added this as calt feature

sub @ALT1 @DEFAULT’ by @ALT2;

But I get the error, any help would be appciciated

You probably put the class name in the class. You add a class and call it DEFAULT in the left list. Than you add “A B” in the text view on the right.

For a description of the OpenType fields, see the handbook, chapter 6.4, page 60.