diff --git a/ice-9/session.scm b/ice-9/session.scm
index c43402efc..3b2abcb9e 100644
--- a/ice-9/session.scm
+++ b/ice-9/session.scm
@@ -123,3 +123,42 @@
   (cond ((procedure? obj) (procedure-source obj))
 	((macro? obj) (procedure-source (macro-transformer obj)))
 	(else #f)))
+
+(define-public (arity obj)
+  (let ((arity (procedure-property obj 'arity)))
+    (display (car arity))
+    (cond ((caddr arity)
+	   (display " or more"))
+	  ((not (zero? (cadr arity)))
+	   (display " required and ")
+	   (display (cadr arity))
+	   (display " optional")))
+    (if (and (not (caddr arity))
+	     (= (car arity) 1)
+	     (<= (cadr arity) 1))
+	(display " argument")
+	(display " arguments"))
+    (if (closure? obj)
+	(let ((formals (cadr (procedure-source obj))))
+	  (if (pair? formals)
+	      (begin
+		(display ": `")
+		(display (car formals))
+		(let loop ((ls (cdr formals)))
+		  (cond ((null? ls)
+			 (display #\'))
+			((not (pair? ls))
+			 (display "', the rest in `")
+			 (display ls)
+			 (display #\'))
+			(else
+			 (if (pair? (cdr ls))
+			     (display "', `")
+			     (display "' and `"))
+			 (display (car ls))
+			 (loop (cdr ls))))))
+	      (begin
+		(display " in `")
+		(display formals)
+		(display #\')))))
+    (display ".\n")))