diff --git a/backend/src/matrix.js b/backend/src/matrix.js
index c8813cb..0167592 100644
--- a/backend/src/matrix.js
+++ b/backend/src/matrix.js
@@ -126,10 +126,20 @@ const start = async () => {
       console.log('error: failed to recover signature:', e.message);
     }
     if (account) {
+      try {
+        const authorAddress = await matrixUserToAuthorAddress.get(event.sender);
+        if (account === authorAddress) {
+          await client.sendNotice(roomId, `Matrix user ${event.sender} already linked to author address ${account}`);
+        } else {
+          await client.sendNotice(roomId, `Matrix user ${event.sender} was linked to author address ${authorAddress}, now linked to ${account}`);
+        }
+      } catch (e) {
+        // Not found
+        await client.sendNotice(roomId, `Registered matrix user ${event.sender} to author address ${account}`);
+      }
       await matrixUserToAuthorAddress.put(event.sender, account);
       await authorAddressToMatrixUser.put(account, event.sender);
     }
-    await client.sendNotice(roomId, `Registered matrix user ${event.sender} to author address ${account}`);
   };
 
   // Before we start the bot, register our command handler