diff --git a/types/auth0-lock/auth0-lock-tests.ts b/types/auth0-lock/auth0-lock-tests.ts
index 6e23e81d5e..53c50dd98f 100644
--- a/types/auth0-lock/auth0-lock-tests.ts
+++ b/types/auth0-lock/auth0-lock-tests.ts
@@ -130,7 +130,8 @@ const otherOptions : Auth0LockConstructorOptions = {
   hashCleanup: false,
   leeway: 30,
   _enableImpersonation: true,
-  _enableIdPInitiatedLogin: false
+  _enableIdPInitiatedLogin: false,
+  defaultADUsernameFromEmailPrefix: false
 };
 
 new Auth0Lock(CLIENT_ID, DOMAIN, otherOptions);
diff --git a/types/auth0-lock/index.d.ts b/types/auth0-lock/index.d.ts
index 2916ec58c8..32a3228e56 100644
--- a/types/auth0-lock/index.d.ts
+++ b/types/auth0-lock/index.d.ts
@@ -130,7 +130,7 @@ interface Auth0LockConstructorOptions {
     closable?: boolean;
     configurationBaseUrl?: string;
     container?: string;
-    defaultADUsernameFromEmailPrefix?: string;
+    defaultADUsernameFromEmailPrefix?: boolean;
     defaultDatabaseConnection?: string;
     defaultEnterpriseConnection?: string;
     flashMessage?: Auth0LockFlashMessageOptions;