diff --git a/packages/core/src/util/ng_dev_mode.ts b/packages/core/src/util/ng_dev_mode.ts
index 3b5c9308be..10bc750635 100644
--- a/packages/core/src/util/ng_dev_mode.ts
+++ b/packages/core/src/util/ng_dev_mode.ts
@@ -82,7 +82,10 @@ export function ngDevModeResetPerfCounters(): NgDevModePerfCounters {
  * The idea is that unless we are doing production build where we explicitly
  * set `ngDevMode == false` we should be helping the developer by providing
  * as much early warning and errors as possible.
+ *
+ * NOTE: changes to the `ngDevMode` name must be synced with the CLI and
+ * possibly other third party tooling. Check with them before altering it.
  */
-if (typeof global['ngDevMode'] === 'undefined' || global['ngDevMode']) {
+if (typeof ngDevMode === 'undefined' || ngDevMode) {
   ngDevModeResetPerfCounters();
 }
diff --git a/packages/core/src/util/ng_i18n_closure_mode.ts b/packages/core/src/util/ng_i18n_closure_mode.ts
index 7ee5abc919..752e4f24bf 100644
--- a/packages/core/src/util/ng_i18n_closure_mode.ts
+++ b/packages/core/src/util/ng_i18n_closure_mode.ts
@@ -12,7 +12,11 @@ declare global {
   const ngI18nClosureMode: boolean;
 }
 
-if (typeof global['ngI18nClosureMode'] === 'undefined') {
+/**
+ * NOTE: changes to the `ngI18nClosureMode` name must be synced with the CLI and
+ * possibly other third party tooling. Check with them before altering it.
+ */
+if (typeof ngI18nClosureMode === 'undefined') {
   // Make sure to refer to ngI18nClosureMode as ['ngI18nClosureMode'] for closure.
   global['ngI18nClosureMode'] =
       // TODO(FW-1250): validate that this actually, you know, works.