Index: sys/kern/kern_sendfile.c
===================================================================
--- sys/kern/kern_sendfile.c	(revision 339339)
+++ sys/kern/kern_sendfile.c	(working copy)
@@ -1006,7 +1006,7 @@
 	fdrop(fp, td);
 
 	if (uap->sbytes != NULL)
-		copyout(&sbytes, uap->sbytes, sizeof(off_t));
+		error = copyout(&sbytes, uap->sbytes, sizeof(off_t));
 
 out:
 	free(hdr_uio, M_IOV);