diff --git a/browser-interface/packages/shared/realm/connections/ArchipelagoConnection.ts b/browser-interface/packages/shared/realm/connections/ArchipelagoConnection.ts
index ad6ca443af..47e9cb7315 100644
--- a/browser-interface/packages/shared/realm/connections/ArchipelagoConnection.ts
+++ b/browser-interface/packages/shared/realm/connections/ArchipelagoConnection.ts
@@ -74,6 +74,10 @@ export async function createArchipelagoConnection(
 
       switch (message.$case) {
         case 'challengeResponse': {
+          if (!message.challengeResponse.challengeToSign.startsWith('dcl-')) {
+            throw new Error('Invalid initial hand-shake')
+          }
+          
           const authChainJson = JSON.stringify(
             Authenticator.signPayload(identity, message.challengeResponse.challengeToSign)
           )