diff --git a/src/Composer/Util/ProcessExecutor.php b/src/Composer/Util/ProcessExecutor.php
index a6664c5a0..3423d9702 100644
--- a/src/Composer/Util/ProcessExecutor.php
+++ b/src/Composer/Util/ProcessExecutor.php
@@ -36,6 +36,9 @@ class ProcessExecutor
     protected $errorOutput;
     protected $io;
 
+    /**
+     * @psalm-var array<int, array<string, mixed>>
+     */
     private $jobs = array();
     private $runningJobs = 0;
     private $maxJobs = 10;
@@ -130,10 +133,8 @@ class ProcessExecutor
      * starts a process on the commandline in async mode
      *
      * @param  string $command the command to execute
-     * @param  mixed  $output  the output will be written into this var if passed by ref
-     *                         if a callable is passed it will be used as output handler
      * @param  string $cwd     the working directory
-     * @return int    statuscode
+     * @return Promise
      */
     public function executeAsync($command, $cwd = null)
     {
@@ -311,6 +312,9 @@ class ProcessExecutor
         $this->runningJobs--;
     }
 
+    /**
+     * @return string[]
+     */
     public function splitLines($output)
     {
         $output = trim($output);