diff --git a/tagtype-notes.md b/tagtype-notes.md
index f527d56..1d03410 100644
--- a/tagtype-notes.md
+++ b/tagtype-notes.md
@@ -64,6 +64,9 @@ rain on a weather forecast.
 
 Optional, if present this is the first version of firmware that supported G5 image compression.
 
+### zlib_compression
+
+Optional, if present this is the first version of firmware that supported zlib image compression.
 
 # Weather Forecast Content type