diff --git a/Storage-backend-compatibility.md b/Storage-backend-compatibility.md
index a4531cb..51a1bdb 100644
--- a/Storage-backend-compatibility.md
+++ b/Storage-backend-compatibility.md
@@ -2,6 +2,7 @@ Some storage backends do not support all the features of S3:
 
 ## Atmos
 
+* does not return meaningful ETag
 * does not support multi-part upload
 
 ## Azure