diff --git a/composer.json b/composer.json
index cfe99ee..d049ec3 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
     "require": {
         "php": ">=5.3",
         "react/event-loop": "^1.0 || ^0.5 || ^0.4 || ^0.3.5",
-        "react/promise": "^2.7.0 || ^1.2.1"
+        "react/promise": "dev-master as 3.0.0 || ^2.7.0 || ^1.2.1"
     },
     "require-dev": {
         "phpunit/phpunit": "^7.0 || ^6.4 || ^5.7 || ^4.8.35"
diff --git a/src/functions.php b/src/functions.php
index 123a905..27cba65 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -2,8 +2,8 @@
 
 namespace React\Promise\Timer;
 
-use React\Promise\CancellablePromiseInterface;
 use React\EventLoop\LoopInterface;
+use React\Promise\CancellablePromiseInterface;
 use React\Promise\PromiseInterface;
 use React\Promise\Promise;
 
@@ -12,7 +12,7 @@ function timeout(PromiseInterface $promise, $time, LoopInterface $loop)
     // cancelling this promise will only try to cancel the input promise,
     // thus leaving responsibility to the input promise.
     $canceller = null;
-    if ($promise instanceof CancellablePromiseInterface) {
+    if ($promise instanceof CancellablePromiseInterface  || \method_exists($promise, 'cancel') === true) {
         // pass promise by reference to clean reference after cancellation handler
         // has been invoked once in order to avoid garbage references in call stack.
         $canceller = function () use (&$promise) {
@@ -48,7 +48,7 @@ function timeout(PromiseInterface $promise, $time, LoopInterface $loop)
 
             // try to invoke cancellation handler of input promise and then clean
             // reference in order to avoid garbage references in call stack.
-            if ($promise instanceof CancellablePromiseInterface) {
+            if ($promise instanceof CancellablePromiseInterface  || \method_exists($promise, 'cancel') === true) {
                 $promise->cancel();
             }
             $promise = null;
diff --git a/tests/FunctionTimeoutTest.php b/tests/FunctionTimeoutTest.php
index 9652d1a..47a7662 100644
--- a/tests/FunctionTimeoutTest.php
+++ b/tests/FunctionTimeoutTest.php
@@ -40,7 +40,7 @@ public function testResolvedWillNotStartTimer()
 
     public function testRejectedWillRejectRightAway()
     {
-        $promise = Promise\reject();
+        $promise = Promise\reject(new \Exception('reject'));
 
         $promise = Timer\timeout($promise, 3, $this->loop);
 
@@ -49,7 +49,7 @@ public function testRejectedWillRejectRightAway()
 
     public function testRejectedWillNotStartTimer()
     {
-        $promise = Promise\reject();
+        $promise = Promise\reject(new \Exception('reject'));
 
         Timer\timeout($promise, 3, $this->loop);
 
@@ -73,10 +73,12 @@ public function testPendingWillRejectOnTimeout()
 
     public function testPendingCancellableWillBeCancelledThroughFollowerOnTimeout()
     {
-        $cancellable = $this->getMockBuilder('React\Promise\CancellablePromiseInterface')->getMock();
+        $cancellableInterface = interface_exists('React\Promise\CancellablePromiseInterface') ?
+            'React\Promise\CancellablePromiseInterface' : 'React\Promise\PromiseInterface';
+        $cancellable = $this->getMockBuilder($cancellableInterface)->getMock();
         $cancellable->expects($this->once())->method('cancel');
 
-        $promise = $this->getMockBuilder('React\Promise\CancellablePromiseInterface')->getMock();
+        $promise = $this->getMockBuilder($cancellableInterface)->getMock();
         $promise->expects($this->once())->method('then')->willReturn($cancellable);
 
         Timer\timeout($promise, 0.01, $this->loop);