diff --git a/docs/gateway/b2.md b/docs/gateway/b2.md
index d9499a5f9..a19509d75 100644
--- a/docs/gateway/b2.md
+++ b/docs/gateway/b2.md
@@ -43,6 +43,7 @@ mc ls myb2
 ### Known limitations
 Gateway inherits the following B2 limitations:
 
+- PutObject() does not return an md5sum of the uploaded file as an etag response.  Apps that check vailidity will fail.
 - No support for CopyObject S3 API (There are no equivalent APIs available on Backblaze B2).
 - No support for CopyObjectPart S3 API (There are no equivalent APIs available on Backblaze B2).
 - Only read-only bucket policy supported at bucket level, all other variations will return API Notimplemented error.