diff --git a/src/lib/es2015.collection.d.ts b/src/lib/es2015.collection.d.ts
index f6087eb4405..74759107851 100644
--- a/src/lib/es2015.collection.d.ts
+++ b/src/lib/es2015.collection.d.ts
@@ -58,7 +58,7 @@ interface ReadonlySet<T> {
     readonly size: number;
 }
 
-interface WeakSet<T> {
+interface WeakSet<T extends object> {
     add(value: T): this;
     delete(value: T): boolean;
     has(value: T): boolean;
diff --git a/src/lib/es2015.iterable.d.ts b/src/lib/es2015.iterable.d.ts
index 26722b5ab2f..ccb7df6be69 100644
--- a/src/lib/es2015.iterable.d.ts
+++ b/src/lib/es2015.iterable.d.ts
@@ -180,7 +180,7 @@ interface SetConstructor {
     new <T>(iterable: Iterable<T>): Set<T>;
 }
 
-interface WeakSet<T> { }
+interface WeakSet<T extends object> { }
 
 interface WeakSetConstructor {
     new <T extends object>(iterable: Iterable<T>): WeakSet<T>;
diff --git a/src/lib/es2015.symbol.wellknown.d.ts b/src/lib/es2015.symbol.wellknown.d.ts
index 23d836c6515..681b6e8edfa 100644
--- a/src/lib/es2015.symbol.wellknown.d.ts
+++ b/src/lib/es2015.symbol.wellknown.d.ts
@@ -118,7 +118,7 @@ interface Set<T> {
     readonly [Symbol.toStringTag]: "Set";
 }
 
-interface WeakSet<T> {
+interface WeakSet<T extends object> {
     readonly [Symbol.toStringTag]: "WeakSet";
 }