diff --git a/systemjs/index.d.ts b/systemjs/index.d.ts
index 013b7b8bea..428e303442 100644
--- a/systemjs/index.d.ts
+++ b/systemjs/index.d.ts
@@ -257,7 +257,7 @@ declare namespace SystemJSLoader {
         /**
          * This represents the System base class, which can be extended or reinstantiated to create a custom System instance.
          */
-        constructor(): System;
+        constructor: new () => System;
 
         /**
          * Deletes a module from the registry by normalized name.
diff --git a/systemjs/systemjs-tests.ts b/systemjs/systemjs-tests.ts
index 0f158d2af4..3c2f8ebadc 100644
--- a/systemjs/systemjs-tests.ts
+++ b/systemjs/systemjs-tests.ts
@@ -35,3 +35,5 @@ System.import('./app.js').then(function (m) {
 System.import('lodash').then(function (_) {
     console.log(_);
 });
+
+const clonedSystemJS = new System.constructor();