diff --git a/packages/core/src/util/is_dev_mode.ts b/packages/core/src/util/is_dev_mode.ts
index 10d2e4554fbe..ae6c9374906f 100644
--- a/packages/core/src/util/is_dev_mode.ts
+++ b/packages/core/src/util/is_dev_mode.ts
@@ -6,6 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {global} from './global';
+
 /**
  * This file is used to control if the default rendering pipeline should be `ViewEngine` or `Ivy`.
  *
@@ -44,5 +46,12 @@ export function enableProdMode(): void {
   if (_runModeLocked) {
     throw new Error('Cannot enable prod mode after platform setup.');
   }
+
+  // The below check is there so when ngDevMode is set via terser
+  // `global['ngDevMode'] = false;` is also dropped.
+  if (typeof ngDevMode === undefined || !!ngDevMode) {
+    global['ngDevMode'] = false;
+  }
+
   _devMode = false;
 }
\ No newline at end of file
diff --git a/packages/zone.js/package.json b/packages/zone.js/package.json
index d1d8c7c4eb28..988d133c3c06 100644
--- a/packages/zone.js/package.json
+++ b/packages/zone.js/package.json
@@ -21,7 +21,7 @@
     "mocha": "^3.1.2",
     "mock-require": "3.0.3",
     "promises-aplus-tests": "^2.1.2",
-    "typescript": "~3.4.2"
+    "typescript": "~3.8.3"
   },
   "scripts": {
     "electrontest": "cd test/extra && node electron.js",