diff --git a/tslib.es6.js b/tslib.es6.js
index bd73dce..8083232 100644
--- a/tslib.es6.js
+++ b/tslib.es6.js
@@ -209,13 +209,20 @@ var __setModuleDefault = Object.create ? (function(o, v) {
     o["default"] = v;
 };
 
-export function __importStar(mod) {
-    if (mod && mod.__esModule) return mod;
-    var result = {};
-    if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
-    __setModuleDefault(result, mod);
-    return result;
-}
+export var __importStar = function (mod) {
+    var cache = typeof WeakMap === "function" ? new WeakMap() : null;
+    __importStar = function (mod) {
+        if (mod === null || (typeof mod !== "object" && typeof mod !== "function")) return { default: mod };
+        if (mod.__esModule) return mod;
+        if (cache && cache.has(mod)) return cache.get(mod);
+        var result = {};
+        for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
+        __setModuleDefault(result, mod);
+        if (cache) cache.set(mod, result);
+        return result;
+    }
+    return __importStar(mod);
+};
 
 export function __importDefault(mod) {
     return (mod && mod.__esModule) ? mod : { default: mod };
diff --git a/tslib.js b/tslib.js
index 4e2462e..8d350de 100644
--- a/tslib.js
+++ b/tslib.js
@@ -251,11 +251,18 @@ var __createBinding;
     };
 
     __importStar = function (mod) {
-        if (mod && mod.__esModule) return mod;
-        var result = {};
-        if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
-        __setModuleDefault(result, mod);
-        return result;
+        var cache = typeof WeakMap === "function" ? new WeakMap() : null;
+        __importStar = function (mod) {
+            if (mod === null || (typeof mod !== "object" && typeof mod !== "function")) return { default: mod };
+            if (mod.__esModule) return mod;
+            if (cache && cache.has(mod)) return cache.get(mod);
+            var result = {};
+            for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
+            __setModuleDefault(result, mod);
+            if (cache) cache.set(mod, result);
+            return result;
+        }
+        return __importStar(mod);
     };
 
     __importDefault = function (mod) {