diff --git a/src/Symfony/Component/EventDispatcher/EventDispatcher.php b/src/Symfony/Component/EventDispatcher/EventDispatcher.php
index c0f839b9db905..fbf69ffe31dec 100644
--- a/src/Symfony/Component/EventDispatcher/EventDispatcher.php
+++ b/src/Symfony/Component/EventDispatcher/EventDispatcher.php
@@ -94,7 +94,7 @@ public function getListeners(string $eventName = null)
     public function getListenerPriority(string $eventName, $listener)
     {
         if (empty($this->listeners[$eventName])) {
-            return null;
+            return 0;
         }
 
         if (\is_array($listener) && isset($listener[0]) && $listener[0] instanceof \Closure && 2 >= \count($listener)) {
@@ -114,7 +114,7 @@ public function getListenerPriority(string $eventName, $listener)
             }
         }
 
-        return null;
+        return 0;
     }
 
     /**
diff --git a/src/Symfony/Component/EventDispatcher/EventDispatcherInterface.php b/src/Symfony/Component/EventDispatcher/EventDispatcherInterface.php
index 88c707c9a360b..8f25e162e06f6 100644
--- a/src/Symfony/Component/EventDispatcher/EventDispatcherInterface.php
+++ b/src/Symfony/Component/EventDispatcher/EventDispatcherInterface.php
@@ -62,7 +62,7 @@ public function getListeners(string $eventName = null);
      *
      * @param callable $listener The listener
      *
-     * @return int|null The event listener priority
+     * @return int The event listener priority, defaults to 0
      */
     public function getListenerPriority(string $eventName, $listener);
 
diff --git a/src/Symfony/Component/EventDispatcher/Tests/EventDispatcherTest.php b/src/Symfony/Component/EventDispatcher/Tests/EventDispatcherTest.php
index ea9fe8c1b6cdc..5d3e4caf1cb09 100644
--- a/src/Symfony/Component/EventDispatcher/Tests/EventDispatcherTest.php
+++ b/src/Symfony/Component/EventDispatcher/Tests/EventDispatcherTest.php
@@ -123,8 +123,8 @@ public function testGetListenerPriority()
 
         $this->assertSame(-10, $this->dispatcher->getListenerPriority('pre.foo', $listener1));
         $this->assertSame(0, $this->dispatcher->getListenerPriority('pre.foo', $listener2));
-        $this->assertNull($this->dispatcher->getListenerPriority('pre.bar', $listener2));
-        $this->assertNull($this->dispatcher->getListenerPriority('pre.foo', function () {}));
+        $this->assertEquals($this->dispatcher->getListenerPriority('pre.bar', $listener2), 0);
+        $this->assertEquals($this->dispatcher->getListenerPriority('pre.foo', function () {}), 0);
     }
 
     public function testDispatch()