diff --git a/app/signatures/page.mdx b/app/signatures/page.mdx
index 2b2c204..0bd1610 100644
--- a/app/signatures/page.mdx
+++ b/app/signatures/page.mdx
@@ -38,7 +38,7 @@ Where:
 - `$0` is the HTTP method (e.g. `GET`, `POST`) in lowercase.
 - `$1` is the path of the request, in standard URI format (don't forget to URL-encode it).
 - `$2` is the nonce, a random string generated by the client.
-- `$3` is the SHA-256 hash of the request body, encoded in base64.
+- `$3` is the SHA-256 hash of the request body, encoded in base64. (if it's a `GET` request, this should be the hash of an empty string)
 
 Sign this string using the user's private key. The resulting signature should be encoded in base64.