diff --git a/README.md b/README.md
index ea5541e..38ab622 100644
--- a/README.md
+++ b/README.md
@@ -318,7 +318,7 @@ $promise = new React\Promise\Promise($resolver, $canceller);
 ```
 
 The promise constructor receives a resolver function and an optional canceller
-function which both will be called with 3 arguments:
+function which both will be called with two arguments:
 
   * `$resolve($value)` - Primary function that seals the fate of the
     returned promise. Accepts either a non-promise value, or another promise.
diff --git a/src/Deferred.php b/src/Deferred.php
index 53d945e..dac6b2b 100644
--- a/src/Deferred.php
+++ b/src/Deferred.php
@@ -12,12 +12,15 @@ final class Deferred
      */
     private $promise;
 
-    /** @var callable */
+    /** @var callable(T):void */
     private $resolveCallback;
 
-    /** @var callable */
+    /** @var callable(\Throwable):void */
     private $rejectCallback;
 
+    /**
+     * @param (callable(callable(T):void,callable(\Throwable):void):void)|null $canceller
+     */
     public function __construct(callable $canceller = null)
     {
         $this->promise = new Promise(function ($resolve, $reject): void {
diff --git a/src/Promise.php b/src/Promise.php
index 1613db5..c46b41f 100644
--- a/src/Promise.php
+++ b/src/Promise.php
@@ -10,13 +10,13 @@
  */
 final class Promise implements PromiseInterface
 {
-    /** @var ?callable */
+    /** @var (callable(callable(T):void,callable(\Throwable):void):void)|null */
     private $canceller;
 
     /** @var ?PromiseInterface<T> */
     private $result;
 
-    /** @var callable[] */
+    /** @var list<callable(PromiseInterface<T>):void> */
     private $handlers = [];
 
     /** @var int */
@@ -25,6 +25,10 @@ final class Promise implements PromiseInterface
     /** @var bool */
     private $cancelled = false;
 
+    /**
+     * @param callable(callable(T):void,callable(\Throwable):void):void $resolver
+     * @param (callable(callable(T):void,callable(\Throwable):void):void)|null $canceller
+     */
     public function __construct(callable $resolver, callable $canceller = null)
     {
         $this->canceller = $canceller;
@@ -57,7 +61,7 @@ public function then(callable $onFulfilled = null, callable $onRejected = null):
 
         return new static(
             $this->resolver($onFulfilled, $onRejected),
-            static function () use (&$parent) {
+            static function () use (&$parent): void {
                 assert($parent instanceof self);
                 --$parent->requiredCancelRequests;
 
@@ -78,7 +82,7 @@ static function () use (&$parent) {
      */
     public function catch(callable $onRejected): PromiseInterface
     {
-        return $this->then(null, static function ($reason) use ($onRejected) {
+        return $this->then(null, static function (\Throwable $reason) use ($onRejected) {
             if (!_checkTypehint($onRejected, $reason)) {
                 return new RejectedPromise($reason);
             }
@@ -92,12 +96,12 @@ public function catch(callable $onRejected): PromiseInterface
 
     public function finally(callable $onFulfilledOrRejected): PromiseInterface
     {
-        return $this->then(static function ($value) use ($onFulfilledOrRejected) {
+        return $this->then(static function ($value) use ($onFulfilledOrRejected): PromiseInterface {
             return resolve($onFulfilledOrRejected())->then(function () use ($value) {
                 return $value;
             });
-        }, static function ($reason) use ($onFulfilledOrRejected) {
-            return resolve($onFulfilledOrRejected())->then(function () use ($reason) {
+        }, static function (\Throwable $reason) use ($onFulfilledOrRejected): PromiseInterface {
+            return resolve($onFulfilledOrRejected())->then(function () use ($reason): RejectedPromise {
                 return new RejectedPromise($reason);
             });
         });
@@ -164,12 +168,12 @@ public function always(callable $onFulfilledOrRejected): PromiseInterface
 
     private function resolver(callable $onFulfilled = null, callable $onRejected = null): callable
     {
-        return function ($resolve, $reject) use ($onFulfilled, $onRejected) {
-            $this->handlers[] = static function (PromiseInterface $promise) use ($onFulfilled, $onRejected, $resolve, $reject) {
+        return function (callable $resolve, callable $reject) use ($onFulfilled, $onRejected): void {
+            $this->handlers[] = static function (PromiseInterface $promise) use ($onFulfilled, $onRejected, $resolve, $reject): void {
                 $promise = $promise->then($onFulfilled, $onRejected);
 
                 if ($promise instanceof self && $promise->result === null) {
-                    $promise->handlers[] = static function (PromiseInterface $promise) use ($resolve, $reject) {
+                    $promise->handlers[] = static function (PromiseInterface $promise) use ($resolve, $reject): void {
                         $promise->then($resolve, $reject);
                     };
                 } else {
@@ -237,6 +241,9 @@ private function unwrap(PromiseInterface $promise): PromiseInterface
         return $promise;
     }
 
+    /**
+     * @param callable(callable(mixed):void,callable(\Throwable):void):void $cb
+     */
     private function call(callable $cb): void
     {
         // Explicitly overwrite argument with null value. This ensure that this
@@ -274,13 +281,13 @@ private function call(callable $cb): void
                 $target =& $this;
 
                 $callback(
-                    static function ($value) use (&$target) {
+                    static function ($value) use (&$target): void {
                         if ($target !== null) {
                             $target->settle(resolve($value));
                             $target = null;
                         }
                     },
-                    static function (\Throwable $reason) use (&$target) {
+                    static function (\Throwable $reason) use (&$target): void {
                         if ($target !== null) {
                             $target->reject($reason);
                             $target = null;
diff --git a/src/functions.php b/src/functions.php
index ac3a66c..2aab877 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -35,7 +35,8 @@ function resolve($promiseOrValue): PromiseInterface
             assert(\is_callable($canceller));
         }
 
-        return new Promise(function ($resolve, $reject) use ($promiseOrValue): void {
+        /** @var Promise<T> */
+        return new Promise(function (callable $resolve, callable $reject) use ($promiseOrValue): void {
             $promiseOrValue->then($resolve, $reject);
         }, $canceller);
     }
@@ -77,7 +78,8 @@ function all(iterable $promisesOrValues): PromiseInterface
 {
     $cancellationQueue = new Internal\CancellationQueue();
 
-    return new Promise(function ($resolve, $reject) use ($promisesOrValues, $cancellationQueue): void {
+    /** @var Promise<array<T>> */
+    return new Promise(function (callable $resolve, callable $reject) use ($promisesOrValues, $cancellationQueue): void {
         $toResolve = 0;
         /** @var bool */
         $continue  = true;
@@ -129,6 +131,7 @@ function race(iterable $promisesOrValues): PromiseInterface
 {
     $cancellationQueue = new Internal\CancellationQueue();
 
+    /** @var Promise<T> */
     return new Promise(function (callable $resolve, callable $reject) use ($promisesOrValues, $cancellationQueue): void {
         $continue = true;
 
@@ -165,7 +168,8 @@ function any(iterable $promisesOrValues): PromiseInterface
 {
     $cancellationQueue = new Internal\CancellationQueue();
 
-    return new Promise(function ($resolve, $reject) use ($promisesOrValues, $cancellationQueue): void {
+    /** @var Promise<T> */
+    return new Promise(function (callable $resolve, callable $reject) use ($promisesOrValues, $cancellationQueue): void {
         $toReject = 0;
         $continue = true;
         $reasons  = [];
diff --git a/tests/Internal/CancellationQueueTest.php b/tests/Internal/CancellationQueueTest.php
index fea5696..e8fd58e 100644
--- a/tests/Internal/CancellationQueueTest.php
+++ b/tests/Internal/CancellationQueueTest.php
@@ -101,6 +101,7 @@ public function rethrowsExceptionsThrownFromCancel(): void
      */
     private function getCancellableDeferred(): Deferred
     {
+        /** @var Deferred<never> */
         return new Deferred($this->expectCallableOnce());
     }
 }
diff --git a/tests/PromiseTest.php b/tests/PromiseTest.php
index 74a1446..34411dc 100644
--- a/tests/PromiseTest.php
+++ b/tests/PromiseTest.php
@@ -19,11 +19,14 @@ public function getPromiseTestAdapter(callable $canceller = null): CallbackPromi
     {
         $resolveCallback = $rejectCallback = null;
 
-        $promise = new Promise(function ($resolve, $reject) use (&$resolveCallback, &$rejectCallback) {
+        $promise = new Promise(function (callable $resolve, callable $reject) use (&$resolveCallback, &$rejectCallback): void {
             $resolveCallback = $resolve;
             $rejectCallback  = $reject;
         }, $canceller);
 
+        assert(is_callable($resolveCallback));
+        assert(is_callable($rejectCallback));
+
         return new CallbackPromiseAdapter([
             'promise' => function () use ($promise) {
                 return $promise;
diff --git a/tests/types/deferred.php b/tests/types/deferred.php
index ffdea72..d468849 100644
--- a/tests/types/deferred.php
+++ b/tests/types/deferred.php
@@ -10,3 +10,40 @@
 $deferredB = new Deferred();
 $deferredB->resolve(42);
 assertType('React\Promise\PromiseInterface<int>', $deferredB->promise());
+
+// $deferred = new Deferred();
+// $deferred->resolve(42);
+// assertType('React\Promise\Deferred<int>', $deferred);
+
+// $deferred = new Deferred();
+// $deferred->resolve(true);
+// $deferred->resolve('ignored');
+// assertType('React\Promise\Deferred<bool>', $deferred);
+
+// $deferred = new Deferred();
+// $deferred->reject(new \RuntimeException());
+// assertType('React\Promise\Deferred<never>', $deferred);
+
+// invalid number of arguments passed to $canceller
+/** @phpstan-ignore-next-line */
+$deferred = new Deferred(function ($a, $b, $c) { });
+assertType('React\Promise\Deferred<mixed>', $deferred);
+
+// invalid types for arguments of $canceller
+/** @phpstan-ignore-next-line */
+$deferred = new Deferred(function (int $a, string $b) { });
+assertType('React\Promise\Deferred<mixed>', $deferred);
+
+// invalid number of arguments passed to $resolve
+$deferred = new Deferred(function (callable $resolve) {
+    /** @phpstan-ignore-next-line */
+    $resolve();
+});
+assertType('React\Promise\Deferred<mixed>', $deferred);
+
+// invalid type passed to $reject
+$deferred = new Deferred(function (callable $resolve, callable $reject) {
+    /** @phpstan-ignore-next-line */
+    $reject(2);
+});
+assertType('React\Promise\Deferred<mixed>', $deferred);
diff --git a/tests/types/promise.php b/tests/types/promise.php
new file mode 100644
index 0000000..fa5b15c
--- /dev/null
+++ b/tests/types/promise.php
@@ -0,0 +1,91 @@
+<?php
+
+use React\Promise\Promise;
+use function PHPStan\Testing\assertType;
+
+// $promise = new Promise(function (): void { });
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// $promise = new Promise(function (callable $resolve): void {
+//     $resolve(42);
+// });
+// assertType('React\Promise\PromiseInterface<int>', $promise);
+
+// $promise = new Promise(function (callable $resolve): void {
+//     $resolve(true);
+//     $resolve('ignored');
+// });
+// assertType('React\Promise\PromiseInterface<bool>', $promise);
+
+// $promise = new Promise(function (callable $resolve, callable $reject): void {
+//     $reject(new \RuntimeException());
+// });
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// $promise = new Promise(function (): never {
+//     throw new \RuntimeException();
+// });
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid number of arguments for $resolver
+/** @phpstan-ignore-next-line */
+$promise = new Promise(function ($a, $b, $c) { });
+assert($promise instanceof Promise);
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid types for arguments of $resolver
+/** @phpstan-ignore-next-line */
+$promise = new Promise(function (int $a, string $b) { });
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid number of arguments passed to $resolve
+$promise = new Promise(function (callable $resolve) {
+    /** @phpstan-ignore-next-line */
+    $resolve();
+});
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid number of arguments passed to $reject
+$promise = new Promise(function (callable $resolve, callable $reject) {
+    /** @phpstan-ignore-next-line */
+    $reject();
+});
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid type passed to $reject
+$promise = new Promise(function (callable $resolve, callable $reject) {
+    /** @phpstan-ignore-next-line */
+    $reject(2);
+});
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid number of arguments for $canceller
+/** @phpstan-ignore-next-line */
+$promise = new Promise(function () { }, function ($a, $b, $c) { });
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid types for arguments of $canceller
+/** @phpstan-ignore-next-line */
+$promise = new Promise(function () { }, function (int $a, string $b) { });
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid number of arguments passed to $resolve
+$promise = new Promise(function () { }, function (callable $resolve) {
+    /** @phpstan-ignore-next-line */
+    $resolve();
+});
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid number of arguments passed to $reject
+$promise = new Promise(function () { }, function (callable $resolve, callable $reject) {
+    /** @phpstan-ignore-next-line */
+    $reject();
+});
+// assertType('React\Promise\PromiseInterface<never>', $promise);
+
+// invalid type passed to $reject
+$promise = new Promise(function() { }, function (callable $resolve, callable $reject) {
+    /** @phpstan-ignore-next-line */
+    $reject(2);
+});
+// assertType('React\Promise\PromiseInterface<never>', $promise);