diff --git a/src/Deferred.php b/src/Deferred.php
index 6bc40293..ef06069f 100644
--- a/src/Deferred.php
+++ b/src/Deferred.php
@@ -36,7 +36,7 @@ public function resolve($value = null)
         \call_user_func($this->resolveCallback, $value);
     }
 
-    public function reject($reason)
+    public function reject(\Throwable $reason)
     {
         $this->promise();
 
diff --git a/src/Promise.php b/src/Promise.php
index 0d75bde3..f25d3667 100644
--- a/src/Promise.php
+++ b/src/Promise.php
@@ -129,7 +129,7 @@ private function resolve($value = null)
         $this->settle(resolve($value));
     }
 
-    private function reject($reason)
+    private function reject(\Throwable $reason)
     {
         if (null !== $this->result) {
             return;
@@ -198,7 +198,7 @@ private function call(callable $callback)
                     function ($value = null) {
                         $this->resolve($value);
                     },
-                    function ($reason) {
+                    function (\Throwable $reason) {
                         $this->reject($reason);
                     }
                 );
diff --git a/src/RejectedPromise.php b/src/RejectedPromise.php
index bfa85655..d256b98f 100644
--- a/src/RejectedPromise.php
+++ b/src/RejectedPromise.php
@@ -62,7 +62,7 @@ public function otherwise(callable $onRejected)
 
     public function always(callable $onFulfilledOrRejected)
     {
-        return $this->then(null, function ($reason) use ($onFulfilledOrRejected) {
+        return $this->then(null, function (\Throwable $reason) use ($onFulfilledOrRejected) {
             return resolve($onFulfilledOrRejected())->then(function () use ($reason) {
                 return new RejectedPromise($reason);
             });
diff --git a/src/functions.php b/src/functions.php
index dea44bf0..4f2dc54f 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -41,19 +41,19 @@ function resolve($promiseOrValue = null)
 }
 
 /**
- * Creates a rejected promise for the supplied `$promiseOrValue`.
+ * Creates a rejected promise for the supplied `$reason`.
  *
- * If `$promiseOrValue` is a value, it will be the rejection value of the
+ * If `$reason` is a value, it will be the rejection value of the
  * returned promise.
  *
- * If `$promiseOrValue` is a promise, its completion value will be the rejected
+ * If `$reason` is a promise, its completion value will be the rejected
  * value of the returned promise.
  *
  * This can be useful in situations where you need to reject a promise without
  * throwing an exception. For example, it allows you to propagate a rejection with
  * the value of another promise.
  *
- * @param \Throwable $promiseOrValue
+ * @param \Throwable $reason
  * @return PromiseInterface
  */
 function reject(\Throwable $reason)
@@ -188,7 +188,7 @@ function some(array $promisesOrValues, $howMany)
                 }
             };
 
-            $rejecter = function ($reason) use ($i, &$reasons, &$toReject, $toResolve, $reject) {
+            $rejecter = function (\Throwable $reason) use ($i, &$reasons, &$toReject, $toResolve, $reject) {
                 if ($toResolve < 1 || $toReject < 1) {
                     return;
                 }
@@ -324,12 +324,8 @@ function fatalError($error)
 /**
  * @internal
  */
-function _checkTypehint(callable $callback, $object)
+function _checkTypehint(callable $callback, \Throwable $reason)
 {
-    if (!\is_object($object)) {
-        return true;
-    }
-
     if (\is_array($callback)) {
         $callbackReflection = new \ReflectionMethod($callback[0], $callback[1]);
     } elseif (\is_object($callback) && !$callback instanceof \Closure) {
@@ -344,11 +340,11 @@ function _checkTypehint(callable $callback, $object)
         return true;
     }
 
-    $expectedException = $parameters[0];
+    $expectedClass = $parameters[0]->getClass();
 
-    if (!$expectedException->getClass()) {
+    if (!$expectedClass) {
         return true;
     }
 
-    return $expectedException->getClass()->isInstance($object);
+    return $expectedClass->isInstance($reason);
 }
diff --git a/tests/FunctionalRejectTest.php b/tests/FunctionalRejectTest.php
deleted file mode 100644
index d303d7a4..00000000
--- a/tests/FunctionalRejectTest.php
+++ /dev/null
@@ -1,37 +0,0 @@
-<?php
-
-namespace React\Promise;
-
-use stdClass;
-
-class FunctionalRejectTest extends TestCase
-{
-    public function nonThrowables()
-    {
-        yield '1' => [1];
-        yield 'true' => [true];
-        yield 'stdClass' => [new stdClass()];
-    }
-
-    /**
-     * @test
-     * @dataProvider nonThrowables
-     */
-    public function shouldThrowWhenCalledWithANonException($input)
-    {
-        $errorCollector = new ErrorCollector();
-        $errorCollector->start();
-
-        (new Promise(function ($_, $reject) use ($input) {
-            $reject($input);
-        }))->done($this->expectCallableNever());
-
-        $errors = $errorCollector->stop();
-
-        $this->assertEquals(E_USER_ERROR, $errors[0]['errno']);
-        $this->assertContains(
-            'TypeError: Argument 1 passed to React\Promise\reject() must implement interface Throwable',
-            $errors[0]['errstr']
-        );
-    }
-}