diff --git a/test-mocha/external_app/external_messaging.spec.ts b/test-mocha/external_app/external_messaging.spec.ts
index 33e6d1b651..d13e342d1d 100644
--- a/test-mocha/external_app/external_messaging.spec.ts
+++ b/test-mocha/external_app/external_messaging.spec.ts
@@ -5,6 +5,9 @@ import {
   InternalMessage,
 } from "../../src/external_app/external_messaging";
 
+// @ts-ignore
+global.__DEV__ = true;
+
 class MockExternalMessaging extends ExternalMessaging {
   public mockSent: InternalMessage[] = [];