diff --git a/README.md b/README.md
index 90d9079..472888d 100644
--- a/README.md
+++ b/README.md
@@ -90,7 +90,7 @@ These go in `config.json`. See also `config.example.json`.
 |prefix|"!"|Prefix for bot commands|
 |relaySmallAttachmentsAsAttachments|false|Whether to relay small attachments from users as native attachments rather than links in modmail threads|
 |requiredAccountAge|None|Required account age for contacting modmail (in hours). If the account is not old enough, a new thread will not be created and the bot will reply with `accountAgeDeniedMessage` (if set) instead.|
-|requiredJoinedAt|None|Required amount of time (in hours) the user must be a member of the server before being able to contact modmail. If the user hasn't been a member of the server for the specified time, a new thread will not be created and the bot will reply with `joinedAtDeniedMessage` (if set) instead.|
+|requiredJoinedAt|None|Required amount of time (in hours) the user must be a member of the server before being able to contact modmail. If the user hasn't been a member of the server for the specified time, a new thread will not be created and the bot will reply with `joinedAtDeniedMessage` (if set) instead. Only works if one main guild has been set.|
 |responseMessage|"Thank you for your message! Our mod team will reply to you here as soon as possible."|The bot's response to DMs that start a new thread|
 |smallAttachmentLimit|2097152|Size limit of `relaySmallAttachmentsAsAttachments`, in bytes (default is 2MB)|
 |snippetPrefix|"!!"|Prefix to use snippets|