diff --git a/tools/gulp/packaging/pure-annotations.ts b/tools/gulp/packaging/pure-annotations.ts
index 615b0e357653..9fa971e4c018 100644
--- a/tools/gulp/packaging/pure-annotations.ts
+++ b/tools/gulp/packaging/pure-annotations.ts
@@ -7,7 +7,7 @@ const classIfeeRegex =
 
 /** Regex that matches downleveled class IIFE expressions with _extends statements */
 const classExtendsIfeeRegex =
-  /^(var (\S+) = )(\(function \(_super\) \{[\n\r]*    __extends\(\2, _super\);[\n\r]*)/gm;
+  /^(var (\S+) = )(\(function \(_super\) {[\n\r]*    tslib.*\.__extends\(\2, _super\);[\n\r]*)/gm;
 
 /**
  * Adds `@__PURE__` annotation comments to IIFEs containing ES5-downleveled classes generated by