diff --git a/io.c b/io.c
index 3e3a0ed448..e4d9f3c4ec 100644
--- a/io.c
+++ b/io.c
@@ -7275,7 +7275,7 @@ io_reopen(VALUE io, VALUE nfile)
             rb_sys_fail(0);
     }
     else {
-	io_tell(fptr);
+	flush_before_seek(fptr);
     }
     if (orig->mode & FMODE_READABLE) {
 	pos = io_tell(orig);