Hello, The attached patched is from Daniel Lloren, I'm just 'a messenger' (and added a comment in the source, preceding the new binding). The proposed patch is to allow exception printers user customization. This has been very important, not to say vital, for those of us who manipulate large structures, lists, arrays, sfri-4 bytevectors, ..., something we have been doing locally ... but we need something for our users (aiscm, guile-cv ...), so they don't have to patch guile locally... (most would be scared to do so and would not do it anyway...). Once applied, users can, for example, customize the raised exception system so it uses truncated-print, either individually (in .guile), or guile admins can do this globally (in share/guile-site/init.scm): (use-modules (ice-9 pretty-print)) (when (defined? 'exception-format) (set! exception-format (lambda (port fmt . args) (for-each (lambda (arg) (truncated-print arg #:port port)) args)))) Maybe there is another/better approach, I don't know, but this works pretty well for me... Thanks, David