diff --git a/lib/index.js b/lib/index.js
index dbb38692d97..b2d4583cf28 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -127,8 +127,8 @@ module.exports = {
         optionalFeaturesMissing ||
         optionalFeatures.isFeatureEnabled('application-template-wrapper')
       ) {
-        this.ui.writeWarnLine(
-          'Setting the `application-template-wrapper` optional feature flag to `true`, or not providing a setting at all, has been deprecated. You must add the `@ember/optional-features` addon and set this feature to `false`. You can also run `npx @ember/octanify` to do this. This warning will become an error in Ember 4.0.0.\n\nFor more information, see the deprecation guide: https://deprecations.emberjs.com/v3.x/#toc_optional-feature-application-template-wrapper'
+        throw new SilentError(
+          'Setting the `application-template-wrapper` optional feature flag to `true`, or not providing a setting at all, was deprecated in Ember 3.x and removed in Ember 4.0.0. You must add the `@ember/optional-features` addon and set this feature to `false`.\n\nFor more information, see the deprecation guide: https://deprecations.emberjs.com/v3.x/#toc_optional-feature-application-template-wrapper'
         );
       }