PROTECT-PORT-OP saves the return value of CLOSE so better return (if #f #f) than (values).

scheme/big/more-port.scm

@@ -182,7 +182,7 @@
    (lambda (ignore)
      (list 'string-input-port))
    (lambda (ignore)
-     (values))
+     (if #f #f))
    (lambda (ignore buffer start needed)
      (eof-object))
    (lambda (port) #f)))