diff --git a/src/CancellationToken.php b/src/CancellationToken.php
index 453062b..1039484 100644
--- a/src/CancellationToken.php
+++ b/src/CancellationToken.php
@@ -11,14 +11,14 @@ interface CancellationToken
      * Subscribes a new handler to be invoked on a cancellation request.
      *
      * This handler might be invoked immediately in case the token has already been cancelled. Returned generators will
-     * automatically be run as coroutines. Any unhandled exceptions will be throw into the event loop.
+     * automatically be run as coroutines. Any unhandled exceptions will be thrown into the event loop.
      *
-     * @param callable(CancelledException) $callback Callback to be invoked on a cancellation request. Will receive a
+     * @param \Closure(CancelledException) $callback Callback to be invoked on a cancellation request. Will receive a
      * `CancelledException` as first argument that may be used to fail the operation's promise.
      *
      * @return string Identifier that can be used to cancel the subscription.
      */
-    public function subscribe(callable $callback): string;
+    public function subscribe(\Closure $callback): string;
 
     /**
      * Unsubscribes a previously registered handler.
diff --git a/src/CombinedCancellationToken.php b/src/CombinedCancellationToken.php
index b1e276c..1f0f4cd 100644
--- a/src/CombinedCancellationToken.php
+++ b/src/CombinedCancellationToken.php
@@ -42,8 +42,7 @@ final class CombinedCancellationToken implements CancellationToken
         }
     }
 
-    /** @inheritdoc */
-    public function subscribe(callable $callback): string
+    public function subscribe(\Closure $callback): string
     {
         $id = $this->nextId++;
 
diff --git a/src/Internal/CancellableToken.php b/src/Internal/CancellableToken.php
index 2cc31fa..8a38996 100644
--- a/src/Internal/CancellableToken.php
+++ b/src/Internal/CancellableToken.php
@@ -37,7 +37,7 @@ final class CancellableToken implements CancellationToken
         }
     }
 
-    public function subscribe(callable $callback): string
+    public function subscribe(\Closure $callback): string
     {
         $id = $this->nextId++;
 
diff --git a/src/Internal/WrappedCancellationToken.php b/src/Internal/WrappedCancellationToken.php
index a7aa8a2..66f9a99 100644
--- a/src/Internal/WrappedCancellationToken.php
+++ b/src/Internal/WrappedCancellationToken.php
@@ -14,7 +14,7 @@ final class WrappedCancellationToken implements CancellationToken
     ) {
     }
 
-    public function subscribe(callable $callback): string
+    public function subscribe(\Closure $callback): string
     {
         return $this->token->subscribe($callback);
     }
diff --git a/src/Internal/functions.php b/src/Internal/functions.php
index b08e005..3678fa8 100644
--- a/src/Internal/functions.php
+++ b/src/Internal/functions.php
@@ -2,21 +2,6 @@
 
 namespace Amp\Internal;
 
-/**
- * @param FutureState $state
- * @param callable    $callback
- *
- * @internal
- */
-function run(FutureState $state, callable $callback): void
-{
-    try {
-        $state->complete($callback());
-    } catch (\Throwable $exception) {
-        $state->error($exception);
-    }
-}
-
 /**
  * Formats a stacktrace obtained via `debug_backtrace()`.
  *
diff --git a/src/NullCancellationToken.php b/src/NullCancellationToken.php
index af263c3..94114c7 100644
--- a/src/NullCancellationToken.php
+++ b/src/NullCancellationToken.php
@@ -27,8 +27,7 @@ namespace Amp;
  */
 final class NullCancellationToken implements CancellationToken
 {
-    /** @inheritdoc */
-    public function subscribe(callable $callback): string
+    public function subscribe(\Closure $callback): string
     {
         return "null-token";
     }
diff --git a/src/TimeoutCancellationToken.php b/src/TimeoutCancellationToken.php
index 2126548..44df5a6 100644
--- a/src/TimeoutCancellationToken.php
+++ b/src/TimeoutCancellationToken.php
@@ -45,10 +45,7 @@ final class TimeoutCancellationToken implements CancellationToken
         EventLoop::cancel($this->watcher);
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function subscribe(callable $callback): string
+    public function subscribe(\Closure $callback): string
     {
         return $this->token->subscribe($callback);
     }
diff --git a/src/functions.php b/src/functions.php
index f1f49ba..470e410 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -18,7 +18,15 @@ use Revolt\EventLoop\UnsupportedFeatureException;
 function launch(callable $callback): Future
 {
     $state = new Internal\FutureState;
-    EventLoop::queue('Amp\\Internal\\run', $state, $callback);
+
+    EventLoop::queue(static function () use ($state, $callback) {
+        try {
+            $state->complete($callback());
+        } catch (\Throwable $exception) {
+            $state->error($exception);
+        }
+    });
+
     return new Future($state);
 }
 
diff --git a/test/CancellationToken/CancellationTest.php b/test/CancellationToken/CancellationTest.php
index 400897a..4a2ff31 100644
--- a/test/CancellationToken/CancellationTest.php
+++ b/test/CancellationToken/CancellationTest.php
@@ -48,7 +48,7 @@ class CancellationTest extends AsyncTestCase
     public function testDoubleCancelOnlyInvokesOnce(): void
     {
         $cancellationSource = new CancellationTokenSource;
-        $cancellationSource->getToken()->subscribe($this->createCallback(1));
+        $cancellationSource->getToken()->subscribe(\Closure::fromCallable($this->createCallback(1)));
 
         $cancellationSource->cancel();
         $cancellationSource->cancel();
@@ -58,6 +58,6 @@ class CancellationTest extends AsyncTestCase
     {
         $cancellationSource = new CancellationTokenSource;
         $cancellationSource->cancel();
-        $cancellationSource->getToken()->subscribe($this->createCallback(1));
+        $cancellationSource->getToken()->subscribe(\Closure::fromCallable($this->createCallback(1)));
     }
 }
diff --git a/test/Future/FutureTest.php b/test/Future/FutureTest.php
index 97a1658..1b5699a 100644
--- a/test/Future/FutureTest.php
+++ b/test/Future/FutureTest.php
@@ -157,7 +157,6 @@ class FutureTest extends AsyncTestCase
         $source->cancel();
     }
 
-
     public function testUnhandledError(): void
     {
         $deferred = new Deferred;
@@ -182,7 +181,7 @@ class FutureTest extends AsyncTestCase
         $deferred->error(new TestException);
         unset($deferred);
 
-        EventLoop::setErrorHandler($this->createCallback(0));
+        EventLoop::setErrorHandler(\Closure::fromCallable($this->createCallback(0)));
     }
 
     public function testIgnoreUnhandledErrorFromFutureError(): void
@@ -191,7 +190,7 @@ class FutureTest extends AsyncTestCase
         $future->ignore();
         unset($future);
 
-        EventLoop::setErrorHandler($this->createCallback(0));
+        EventLoop::setErrorHandler(\Closure::fromCallable($this->createCallback(0)));
     }
 
     public function testMapWithCompleteFuture(): void
@@ -294,6 +293,7 @@ class FutureTest extends AsyncTestCase
         $future = $future->finally(static fn () => Future::complete()->await());
         self::assertSame(1, $future->await());
     }
+
     public function testFinallyWithPendingFuture(): void
     {
         $deferred = new Deferred;
@@ -319,16 +319,16 @@ class FutureTest extends AsyncTestCase
      * @template T
      *
      * @param float $seconds
-     * @param T $value
+     * @param T     $value
      *
      * @return Future<T>
      */
     private function delay(float $seconds, mixed $value): Future
     {
         return launch(
-            /**
-             * @return T
-             */
+        /**
+         * @return T
+         */
             static function () use ($seconds, $value): mixed {
                 delay($seconds);
                 return $value;