diff --git a/tslib.es6.js b/tslib.es6.js
index 063e8c8..87a3875 100644
--- a/tslib.es6.js
+++ b/tslib.es6.js
@@ -226,7 +226,7 @@ export function __importStar(mod) {
 }
 
 export function __importDefault(mod) {
-    return (mod && mod.__esModule) ? mod : { default: mod };
+    return (mod && mod.__esModule && mod.default) ? mod : { default: mod };
 }
 
 export function __classPrivateFieldGet(receiver, state, kind, f) {
diff --git a/tslib.js b/tslib.js
index fd9a852..b3f9d6e 100644
--- a/tslib.js
+++ b/tslib.js
@@ -268,7 +268,7 @@ var __createBinding;
     };
 
     __importDefault = function (mod) {
-        return (mod && mod.__esModule) ? mod : { "default": mod };
+        return (mod && mod.__esModule && mod.default) ? mod : { "default": mod };
     };
 
     __classPrivateFieldGet = function (receiver, state, kind, f) {