diff --git a/src/PromiseInterface.php b/src/PromiseInterface.php
index 422f9f16..d80d1142 100644
--- a/src/PromiseInterface.php
+++ b/src/PromiseInterface.php
@@ -4,5 +4,8 @@
 
 interface PromiseInterface
 {
+    /**
+     * @return PromiseInterface
+     */
     public function then(callable $onFulfilled = null, callable $onRejected = null, callable $onProgress = null);
 }
diff --git a/src/PromisorInterface.php b/src/PromisorInterface.php
index b53c00ae..9341a4fa 100644
--- a/src/PromisorInterface.php
+++ b/src/PromisorInterface.php
@@ -4,5 +4,8 @@
 
 interface PromisorInterface
 {
+    /**
+     * @return PromiseInterface
+     */
     public function promise();
 }