diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 816e709afa5612941fa1241cf21c768710f51282..082da38762fc7c01e0d6a53810d3bc0160e86caf 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -962,11 +962,14 @@ static inline ssize_t do_tty_write(
 		if (ret <= 0)
 			break;
 
+		written += ret;
+		if (ret > size)
+			break;
+
 		/* FIXME! Have Al check this! */
 		if (ret != size)
 			iov_iter_revert(from, size-ret);
 
-		written += ret;
 		count -= ret;
 		if (!count)
 			break;