diff --git a/docs.wrm/api/signer.wrm b/docs.wrm/api/signer.wrm
index 12069a2d20..b0f47eaafc 100644
--- a/docs.wrm/api/signer.wrm
+++ b/docs.wrm/api/signer.wrm
@@ -74,6 +74,12 @@ _property: signer.signMessage(message) => Promise<string<[RawSignature](signatur
 This returns a Promise which resolves to the [[signature-raw]]
 of //message//.
 
+A signed message is prefixd with ``"\\x19Ethereum signed message:\\n"`` and
+the length of the message, using the [hashMessage](utils-hashMessage)
+method, so that it is [EIP-191](link-eip-191) compliant. If recovering
+the address in Solidity, this prefix will be required to create a matching
+hash.
+
 Sub-classes **must** implement this, however they may throw if signing a
 message is not supported, such as in a Contract-based Wallet or
 Meta-Transaction-based Wallet.