diff --git a/packages/auth-auth0/index.ts b/packages/auth-auth0/index.ts
index 9f16265..1830d7a 100644
--- a/packages/auth-auth0/index.ts
+++ b/packages/auth-auth0/index.ts
@@ -13,6 +13,7 @@ type E = ReturnType<ReturnType<typeof prepareEffects>>
 declare module '@hydrofoil/shell-auth' {
   interface AuthState {
     auth0: Auth0Client
+    referrer?: string
   }
 
   // eslint-disable-next-line