diff --git a/tagtype-notes.md b/tagtype-notes.md
index 94bae52..f527d56 100644
--- a/tagtype-notes.md
+++ b/tagtype-notes.md
@@ -60,6 +60,11 @@ rain on a weather forecast.
 |27| Day Ahead|
 |28| tag command|
 
+### g5_compression
+
+Optional, if present this is the first version of firmware that supported G5 image compression.
+
+
 # Weather Forecast Content type
 
 Example from tagtype 05.json: