diff --git a/src/lib/es2021.weakref.d.ts b/src/lib/es2021.weakref.d.ts
index dd6f4a37056..b0f1d87570e 100644
--- a/src/lib/es2021.weakref.d.ts
+++ b/src/lib/es2021.weakref.d.ts
@@ -42,7 +42,7 @@ interface FinalizationRegistry<T> {
      * @param unregisterToken The token that was used as the unregisterToken argument when calling
      * register to register the target value.
      */
-    unregister(unregisterToken: WeakKey): void;
+    unregister(unregisterToken: WeakKey): boolean;
 }
 
 interface FinalizationRegistryConstructor {
diff --git a/tests/baselines/reference/acceptSymbolAsWeakType.types b/tests/baselines/reference/acceptSymbolAsWeakType.types
index dee19abb1c2..f55e0cd439f 100644
--- a/tests/baselines/reference/acceptSymbolAsWeakType.types
+++ b/tests/baselines/reference/acceptSymbolAsWeakType.types
@@ -168,14 +168,14 @@ f.register(s, null);
 >  : ^^^^^^
 
 f.unregister(s);
->f.unregister(s) : void
->                : ^^^^
->f.unregister : (unregisterToken: WeakKey) => void
->             : ^               ^^       ^^^^^^^^^
+>f.unregister(s) : boolean
+>                : ^^^^^^^
+>f.unregister : (unregisterToken: WeakKey) => boolean
+>             : ^               ^^       ^^^^^^^^^^^^
 >f : FinalizationRegistry<unknown>
 >  : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
->unregister : (unregisterToken: WeakKey) => void
->           : ^               ^^       ^^^^^^^^^
+>unregister : (unregisterToken: WeakKey) => boolean
+>           : ^               ^^       ^^^^^^^^^^^^
 >s : symbol
 >  : ^^^^^^
 
diff --git a/tests/baselines/reference/dissallowSymbolAsWeakType.types b/tests/baselines/reference/dissallowSymbolAsWeakType.types
index 67dbc4a338f..2701bd3f57f 100644
--- a/tests/baselines/reference/dissallowSymbolAsWeakType.types
+++ b/tests/baselines/reference/dissallowSymbolAsWeakType.types
@@ -168,14 +168,14 @@ f.register(s, null);
 >  : ^^^^^^
 
 f.unregister(s);
->f.unregister(s) : void
->                : ^^^^
->f.unregister : (unregisterToken: WeakKey) => void
->             : ^               ^^       ^^^^^^^^^
+>f.unregister(s) : boolean
+>                : ^^^^^^^
+>f.unregister : (unregisterToken: WeakKey) => boolean
+>             : ^               ^^       ^^^^^^^^^^^^
 >f : FinalizationRegistry<unknown>
 >  : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
->unregister : (unregisterToken: WeakKey) => void
->           : ^               ^^       ^^^^^^^^^
+>unregister : (unregisterToken: WeakKey) => boolean
+>           : ^               ^^       ^^^^^^^^^^^^
 >s : symbol
 >  : ^^^^^^
 
diff --git a/tests/baselines/reference/esNextWeakRefs_IterableWeakMap.types b/tests/baselines/reference/esNextWeakRefs_IterableWeakMap.types
index 659f10fbe26..2aee7c76d4e 100644
--- a/tests/baselines/reference/esNextWeakRefs_IterableWeakMap.types
+++ b/tests/baselines/reference/esNextWeakRefs_IterableWeakMap.types
@@ -357,16 +357,16 @@ export class IterableWeakMap<K extends object, V> implements WeakMap<K, V> {
 >    : ^^^^^^^^^^
 
         this.#finalizationGroup.unregister(ref);
->this.#finalizationGroup.unregister(ref) : void
->                                        : ^^^^
->this.#finalizationGroup.unregister : (unregisterToken: WeakKey) => void
->                                   : ^               ^^       ^^^^^^^^^
+>this.#finalizationGroup.unregister(ref) : boolean
+>                                        : ^^^^^^^
+>this.#finalizationGroup.unregister : (unregisterToken: WeakKey) => boolean
+>                                   : ^               ^^       ^^^^^^^^^^^^
 >this.#finalizationGroup : FinalizationRegistry<{ readonly ref: WeakRef<object>; readonly set: Set<WeakRef<object>>; }>
 >                        : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 >this : this
 >     : ^^^^
->unregister : (unregisterToken: WeakKey) => void
->           : ^               ^^       ^^^^^^^^^
+>unregister : (unregisterToken: WeakKey) => boolean
+>           : ^               ^^       ^^^^^^^^^^^^
 >ref : WeakRef<K>
 >    : ^^^^^^^^^^