Hi, it's a pattern matching failure in tag_module_type, which means the file stdLabels.mli contains some module type that I didn't know about when I wrote tag_module_type.
As a quick solution you can add a catch-all line | _ -> () to tag_module_type. This will hopefully fix the bug, but you won't get tags for the offending module type. If somebody could send me that stdLabels.mli (or include it here in the bug report) I will try to take a look. (When I wrote otags, I explicitly avoided catch-all clauses. This way I could check at compile time that I covered all existing syntax. You are paying the price for this now - sorry for that. You may add catch-all clauses to all functions in tags.ml to avoid crashes like this one for new syntax constructs.) Bye, Hendrik