diff --git a/types/ServerMessage.ts b/ServerMessage.ts
similarity index 87%
rename from types/ServerMessage.ts
rename to ServerMessage.ts
index e6bd9cc..69510a3 100644
--- a/types/ServerMessage.ts
+++ b/ServerMessage.ts
@@ -4,6 +4,7 @@ export enum MessageType {
 }
 
 export type ServerMessage = {
+  __ctx?: string;
   type: MessageType;
   date: number;
 };
@@ -31,6 +32,13 @@ export function isServerMessage(
   ) {
     return false;
   }
+  if (
+    Object.hasOwnProperty.call(obj, "__ctx") &&
+    typeof (obj as { __ctx: unknown }).__ctx !== "string" &&
+    typeof (obj as { __ctx: unknown }).__ctx !== "undefined"
+  ) {
+    return false;
+  }
 
   return true;
 }