diff --git a/src/React/Promise/DeferredPromise.php b/src/React/Promise/DeferredPromise.php
index ea63cb38..05f95f4c 100644
--- a/src/React/Promise/DeferredPromise.php
+++ b/src/React/Promise/DeferredPromise.php
@@ -2,7 +2,7 @@
 
 namespace React\Promise;
 
-class DeferredPromise implements PromiseInterface
+class DeferredPromise implements PromiseInterface, CancellablePromiseInterface
 {
     private $deferred;