diff --git a/hws/spotify_playlists/README.md b/hws/spotify_playlists/README.md
index 4068b39..62d3ed6 100644
--- a/hws/spotify_playlists/README.md
+++ b/hws/spotify_playlists/README.md
@@ -122,6 +122,10 @@ When playlist_tiny1.txt and actions1.txt are supplied to your program as the two
 "Viva La Vida" Coldplay
 ```
 
+## Non-existence Songs
+
+If a move action or a remove action as defined in the **actions file** attempts to move or remove a song which does not exist in the playlist, your program should ignore such an action.
+
 <!-- ### Command 1: add a music track to a playlist
 The first argument is the name of an input file which contains a playlist - in this README, we will refer to this file as the **playlist file**. The second argument is the name of another input file which contains all available music tracks - in this README, we will refer to this file as the **library file**. The third argument is the output file. The fourth argument is the action, which in this case is "add". The fifth argument is the title of the music track.