diff --git a/doc/lightning-invoice.7.txt b/doc/lightning-invoice.7.txt
index 38910707e..9f49cf358 100644
--- a/doc/lightning-invoice.7.txt
+++ b/doc/lightning-invoice.7.txt
@@ -19,13 +19,14 @@ lightning daemon can use to pay this invoice.
 The 'msatoshi' can be the string "any", which creates an invoice
 that can be paid with any amount.
 
-The 'label' must be unique; it is never revealed to other nodes on
+The 'label' must be a unique string; it is never revealed to other nodes on
 the lightning network, but it can be used to query the status of this
 invoice.
 
 The 'description' is a short description of purpose of payment,
 e.g. '1 cup of coffee'. This value is encoded into the BOLT11 invoice
-and is viewable by any node you send this invoice to.
+and is viewable by any node you send this invoice to.  It must be
+UTF-8, and cannot use '\u' JSON escape codes.
 
 The 'expiry' is optionally the number of seconds the invoice is valid for.
 If no value is provided the default of 3600 (1 Hour) is used.