diff --git a/Sources/PenguinParallel/ConcurrencyPlatform.swift b/Sources/PenguinParallel/ConcurrencyPlatform.swift
index 1209c4b3..28e18e83 100644
--- a/Sources/PenguinParallel/ConcurrencyPlatform.swift
+++ b/Sources/PenguinParallel/ConcurrencyPlatform.swift
@@ -146,6 +146,8 @@ public protocol RawThreadLocalStorage {
 
   /// Makes a new key; the returned key should be used for the entire process lifetime.
   static func makeKey() -> Key
+  /// Invalidates a previously constructed key, freeing resources
+  static func destroyKey(_ key: inout Key)
   /// Retrieves the raw pointer associated with the given key.
   static func get(for key: Key) -> UnsafeMutableRawPointer?
   /// Sets the raw pointer associated with the given key.
@@ -158,7 +160,7 @@ public struct TypedThreadLocalStorage<Underlying: RawThreadLocalStorage> {
 
   /// Token used to index into the thread local storage.
   public struct Key<Value: AnyObject> {
-    fileprivate let key: Underlying.Key
+    fileprivate var key: Underlying.Key
 
     /// The thread-local value associated with `self`.
     public var localValue: Value? {
@@ -176,6 +178,11 @@ public struct TypedThreadLocalStorage<Underlying: RawThreadLocalStorage> {
     Key(key: Underlying.makeKey())
   }
 
+  /// Deallocates a key for type `T`.
+  public static func destroyKey<T: AnyObject>(_ key: inout Key<T>) {
+    Underlying.destroyKey(&key.key)
+  }
+
   /// Retrieves the thread-local value for `key`, if it exists.
   public static func get<T: AnyObject>(_ key: Key<T>) -> T? {
     guard let ptr = Underlying.get(for: key.key) else { return nil }
diff --git a/Sources/PenguinParallel/ThreadLocalStorage.swift b/Sources/PenguinParallel/ThreadLocalStorage.swift
index a2f6c117..cd768918 100644
--- a/Sources/PenguinParallel/ThreadLocalStorage.swift
+++ b/Sources/PenguinParallel/ThreadLocalStorage.swift
@@ -59,6 +59,15 @@ public struct PosixThreadLocalStorage: RawThreadLocalStorage {
     Key()
   }
 
+  public static func destroyKey(_ key: inout Key) {
+    #if os(Windows)
+      fatalError("Unimplemented!")
+    #else
+      pthread_key_delete(key.value)
+      key.value = 0
+    #endif
+  }
+
   public static func get(for key: Key) -> UnsafeMutableRawPointer? {
     pthread_getspecific(key.value)
   }