diff --git a/ForumClient.markdown b/ForumClient.markdown
index cbd05e2..c6fbdd8 100644
--- a/ForumClient.markdown
+++ b/ForumClient.markdown
@@ -22,7 +22,7 @@ The client identifer is random:
 
 If `author` is null, the post is anonymous and `signature` must also be null. Otherwise `author` is a list with two elements: `name` (string) and `public_key` (raw).
 
-If `signature` is null, the post is anonymous and `author` must also be null. Otherwise `signature` is a signature with `public_key`, calculated over a list with five elements: `app_id` (raw), `forum` (list), `author` (list), `content` (list), and `timestamp` (int). `app_id` is the application identifier. `forum`, `author` and `content` are described above. `timestamp` is the timestamp from the [message header](BSP#message-format).
+If `signature` is null, the post is anonymous and `author` must also be null. Otherwise `signature` is a signature with `public_key`, calculated over a list with five elements: `client_id` (raw), `forum` (list), `author` (list), `content` (list), and `timestamp` (int). `client_id` is the client identifier. `forum`, `author` and `content` are described above. `timestamp` is the timestamp from the [message header](BSP#message-format).
 
 **4: ATTACHMENT** - The content is raw data.