diff --git a/docs/proposed/http-storage-node-protocol.rst b/docs/proposed/http-storage-node-protocol.rst
index f6d90526e..f9f2cd868 100644
--- a/docs/proposed/http-storage-node-protocol.rst
+++ b/docs/proposed/http-storage-node-protocol.rst
@@ -436,6 +436,7 @@ Encoding
 ~~~~~~~~
 
 * ``storage_index`` MUST be `Base32`_ encoded in URLs.
+* ``share_number`` MUST be a decimal representation
 
 General
 ~~~~~~~