diff --git a/types/es6-shim/index.d.ts b/types/es6-shim/index.d.ts
index f310cfc231..99268a905e 100644
--- a/types/es6-shim/index.d.ts
+++ b/types/es6-shim/index.d.ts
@@ -593,7 +593,7 @@ interface SetConstructor {
 
 declare var Set: SetConstructor;
 
-interface WeakMap<K extends Object, V> {
+interface WeakMap<K extends object, V> {
     delete(key: K): boolean;
     get(key: K): V | undefined;
     has(key: K): boolean;
@@ -601,8 +601,8 @@ interface WeakMap<K extends Object, V> {
 }
 
 interface WeakMapConstructor {
-    new <K extends Object, V>(): WeakMap<K, V>;
-    new <K extends Object, V>(iterable: IterableShim<[K, V]>): WeakMap<K, V>;
+    new <K extends object, V>(): WeakMap<K, V>;
+    new <K extends object, V>(iterable: IterableShim<[K, V]>): WeakMap<K, V>;
     prototype: WeakMap<any, any>;
 }