Index: chicken/iup-base.scm
==================================================================
--- chicken/iup-base.scm
+++ chicken/iup-base.scm
@@ -316,11 +316,11 @@
 	(define frame-return/handle!
 		(foreign-lambda* void ([c-pointer frame] [ihandle ret]) "va_return_ptr((va_alist)frame, Ihandle *, ret);"))
 	
 	(call-with-current-continuation
 	 (lambda (return)
-		 (let ([sig "i"] [ret 'continue])
+		 (let ([sig "i"] [ret? #f])
 			 (dynamic-wind
 				 void
 				 (lambda ()
 					 (let* ([data (registry-ref (pointer->address cid))]
 									[proc (cdr data)])
@@ -340,21 +340,27 @@
 														 [(#\s) (frame-arg/string! frame)]
 														 [(#\v) (frame-arg/pointer! frame)]
 														 [(#\h) (frame-arg/handle! frame)]))])
 							 (handle-exceptions exn
 								 (print-error-message exn (current-error-port) "Error: in callback")
-								 (set! ret (apply proc args))))))
+								 (let ([ret (apply proc args)])
+									 (case (string-ref sig 0)
+										 [(#\b) (frame-return/ubyte! frame ret)]
+										 [(#\i) (frame-return/status! frame ret)]
+										 [(#\f) (frame-return/float! frame ret)]
+										 [(#\d) (frame-return/double! frame ret)]
+										 [(#\v) (frame-return/pointer! frame ret)]
+										 [(#\h) (frame-return/handle! frame ret)])
+									 (set! ret? #t))))))
 				 (lambda ()
-					 (handle-exceptions exn
-						 (void)
+					 (unless ret?
 						 (case (string-ref sig 0)
-							 [(#\b) (frame-return/ubyte! frame ret)]
-							 [(#\i) (frame-return/status! frame ret)]
-							 [(#\f) (frame-return/float! frame ret)]
-							 [(#\d) (frame-return/double! frame ret)]
-							 [(#\v) (frame-return/pointer! frame ret)]
-							 [(#\h) (frame-return/handle! frame ret)]))
+							 [(#\b) (frame-return/ubyte! frame 0)]
+							 [(#\i) (frame-return/status! frame 'continue)]
+							 [(#\f) (frame-return/float! frame 0.0)]
+							 [(#\d) (frame-return/double! frame 0.0)]
+							 [(#\v #\h) (frame-return/pointer! frame #f)]))
 					 (return (void))))))))
 
 (define-values (callback-set! callback)
 	(letrec ([signature/raw
 						(foreign-lambda* c-string ([nonnull-ihandle handle] [iname/upcase name])