Index: sendfile.scm
===================================================================
--- sendfile.scm	(revision 18279)
+++ sendfile.scm	(working copy)
@@ -292,7 +292,7 @@
     (let* ((buffsize (read-write-buffer-size))
            (buffer (make-string buffsize))
            (write-timeout (write-timeout))
-           (write/offset (foreign-lambda* int ((int dst) (c-string buff) (unsigned-integer offset) (unsigned-integer bytes))
+           (write/offset (foreign-lambda* int ((int dst) (nonnull-scheme-pointer buff) (unsigned-integer offset) (unsigned-integer bytes))
                                           "C_return(write(dst,buff + offset,bytes));"))
            (write-bytes (lambda (size)
                           (let loop ((left size) (offset 0))