diff --git a/composer.json b/composer.json
index f1ed7cf..268e784 100644
--- a/composer.json
+++ b/composer.json
@@ -23,6 +23,7 @@
         "phpunit/phpunit": "^5.7"
     },
     "require": {
+        "php": ">=5.4",
         "league/tactician": "^1.0"
     }
 }
diff --git a/src/EventDispatcher/ContainsListenersInterface.php b/src/EventDispatcher/ContainsListenersInterface.php
new file mode 100644
index 0000000..b2da221
--- /dev/null
+++ b/src/EventDispatcher/ContainsListenersInterface.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace BornFree\TacticianDomainEvent\EventDispatcher;
+
+interface ContainsListenersInterface
+{
+    /**
+     * @param $eventName
+     * @param callable $listener
+     * @return mixed
+     */
+    public function addListener($eventName, callable $listener);
+
+    /**
+     * @param string $eventName
+     * @return callable[]
+     */
+    public function getListeners($eventName);
+
+    /**
+     * @param string $eventName
+     * @return bool
+     */
+    public function hasListeners($eventName);
+}
\ No newline at end of file
diff --git a/src/EventDispatcher/EventDispatcher.php b/src/EventDispatcher/EventDispatcher.php
index 7190ae3..96258c0 100644
--- a/src/EventDispatcher/EventDispatcher.php
+++ b/src/EventDispatcher/EventDispatcher.php
@@ -2,8 +2,7 @@
 
 namespace BornFree\TacticianDomainEvent\EventDispatcher;
 
-
-class EventDispatcher implements EventDispatcherInterface
+class EventDispatcher implements EventDispatcherInterface, ContainsListenersInterface
 {
     /**
      * @var callable[][]
@@ -23,8 +22,7 @@ public function dispatch($event)
     }
 
     /**
-     * @param string $eventName
-     * @param callable $listener
+     * @inheritdoc
      */
     public function addListener($eventName, callable $listener)
     {
@@ -32,8 +30,7 @@ public function addListener($eventName, callable $listener)
     }
 
     /**
-     * @param string $eventName
-     * @return callable[]
+     * @inheritdoc
      */
     public function getListeners($eventName)
     {
@@ -45,8 +42,7 @@ public function getListeners($eventName)
     }
 
     /**
-     * @param string $eventName
-     * @return bool
+     * @inheritdoc
      */
     public function hasListeners($eventName)
     {