diff --git a/src/Composer/Console/Application.php b/src/Composer/Console/Application.php
index 2701e118fd15..c2d15ca5bfda 100644
--- a/src/Composer/Console/Application.php
+++ b/src/Composer/Console/Application.php
@@ -119,7 +119,7 @@ public function __construct()
     /**
      * @inheritDoc
      */
-    public function run(InputInterface $input = null, OutputInterface $output = null)
+    public function run(InputInterface $input = null, OutputInterface $output = null): int
     {
         if (null === $output) {
             $output = Factory::createOutput();