diff --git a/integration/side-effects/snapshots/core/esm2015.js b/integration/side-effects/snapshots/core/esm2015.js
index d12748503d..13a1af3941 100644
--- a/integration/side-effects/snapshots/core/esm2015.js
+++ b/integration/side-effects/snapshots/core/esm2015.js
@@ -12,6 +12,6 @@ const __global = "undefined" !== typeof global && global;
 
 const _global = __globalThis || __global || __window || __self;
 
-if (ngDevMode) _global.$localize = _global.$localize || function() {
+if ("undefined" !== typeof ngDevMode && ngDevMode) _global.$localize = _global.$localize || function() {
     throw new Error("It looks like your application or one of its dependencies is using i18n.\n" + "Angular 9 introduced a global `$localize()` function that needs to be loaded.\n" + "Please run `ng add @angular/localize` from the Angular CLI.\n" + "(For non-CLI projects, add `import '@angular/localize/init';` to your `polyfills.ts` file.\n" + "For server-side rendering applications add the import to your `main.server.ts` file.)");
 };
diff --git a/packages/core/src/core.ts b/packages/core/src/core.ts
index 019394da77..b59aabbbe1 100644
--- a/packages/core/src/core.ts
+++ b/packages/core/src/core.ts
@@ -38,7 +38,7 @@ export {Sanitizer} from './sanitization/sanitizer';
 export * from './codegen_private_exports';
 
 import {global} from './util/global';
-if (ngDevMode) {
+if (typeof ngDevMode !== 'undefined' && ngDevMode) {
   // This helper is to give a reasonable error message to people upgrading to v9 that have not yet
   // installed `@angular/localize` in their app.
   // tslint:disable-next-line: no-toplevel-property-access