diff --git a/bip-0322.mediawiki b/bip-0322.mediawiki
index 81ef896d3..440602f7e 100644
--- a/bip-0322.mediawiki
+++ b/bip-0322.mediawiki
@@ -80,6 +80,8 @@ A full signature consists of the base64-encoding of the to_sign
tra
A signer may construct a proof of funds, demonstrating control of a set of UTXOs, by constructing a full signature as above, with the following modifications.
+* message_challenge
is unused and shall be set to OP_TRUE
+* Similarly, message_signature
is then empty.
* All outputs that the signer wishes to demonstrate control of are included as additional inputs of to_sign
, and their witness and scriptSig data should be set as though these outputs were actually being spent.
Unlike an ordinary signature, validators of a proof of funds need access to the current UTXO set, to learn that the claimed inputs exist on the blockchain, and to learn their scriptPubKeys.