Sorry I posted a version of session.scm with a prtly fix included
anyway here is a patch where we add allow-other-keys?
diff --git a/module/ice-9/session.scm b/module/ice-9/session.scm
index fbb03d2..dc2c927 100644
--- a/module/ice-9/session.scm
+++ b/module/ice-9/session.scm
@@ -504,13 +504,14 @@ It is an image under the mapping EXTRACT."
if the information cannot be obtained.
The alist keys that are currently defined are `required', `optional',
-`keyword', and `rest'."
+`keyword', allow-other-keys? and `rest'."
(cond
((procedure-property proc 'arglist)
=> (lambda (arglist)
`((required . ,(car arglist))
(optional . ,(cadr arglist))
(keyword . ,(caddr arglist))
+ (allow-other-keys? . ,(cadddr arglist))
(rest . ,(car (cddddr arglist))))))
((procedure-source proc)
=> cadr)
