diff --git a/Custom-Post-Processing-Scripts.md b/Custom-Post-Processing-Scripts.md
index 49d6de4..e73866b 100644
--- a/Custom-Post-Processing-Scripts.md
+++ b/Custom-Post-Processing-Scripts.md
@@ -27,6 +27,7 @@ Radarr can execute a custom script when new movies are imported or a movie is re
 | Environment Variable | Details |
 |---|---|
 | radarr_eventtype | Download |
+| radarr_isupgrade | `True` when an existing file is upgraded, otherwise `False`
 | radarr_movie_id | Internal ID of the movie |
 | radarr_movie_title | Title of the movie |
 | radarr_movie_path | Full path to the movie ( /Movie (Year)/ ) |