diff --git a/types/npm-package-arg/index.d.ts b/types/npm-package-arg/index.d.ts
index fde2710f23..0aa0d7f28e 100644
--- a/types/npm-package-arg/index.d.ts
+++ b/types/npm-package-arg/index.d.ts
@@ -2,6 +2,7 @@
 // Project: https://github.com/npm/npm-package-arg
 // Definitions by: Melvin Groenhoff <https://github.com/mgroenhoff>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 2.1
 
 /**
  * Throws if the package name is invalid, a dist-tag is invalid or a URL's protocol is not supported.