diff --git a/src/Composer/SelfUpdate/Keys.php b/src/Composer/SelfUpdate/Keys.php
index a8f02e3e2..808b8766d 100644
--- a/src/Composer/SelfUpdate/Keys.php
+++ b/src/Composer/SelfUpdate/Keys.php
@@ -17,6 +17,11 @@ namespace Composer\SelfUpdate;
  */
 class Keys
 {
+    /**
+     * @param string $path
+     *
+     * @return string
+     */
     public static function fingerprint($path)
     {
         $hash = strtoupper(hash('sha256', preg_replace('{\s}', '', file_get_contents($path))));
diff --git a/src/Composer/SelfUpdate/Versions.php b/src/Composer/SelfUpdate/Versions.php
index 591c11253..9e617fb13 100644
--- a/src/Composer/SelfUpdate/Versions.php
+++ b/src/Composer/SelfUpdate/Versions.php
@@ -38,6 +38,9 @@ class Versions
         $this->config = $config;
     }
 
+    /**
+     * @return string
+     */
     public function getChannel()
     {
         if ($this->channel) {
@@ -55,6 +58,11 @@ class Versions
         return $this->channel = 'stable';
     }
 
+    /**
+     * @param string $channel
+     *
+     * @return void
+     */
     public function setChannel($channel)
     {
         if (!in_array($channel, self::$channels, true)) {
@@ -66,6 +74,11 @@ class Versions
         file_put_contents($channelFile, (is_numeric($channel) ? 'stable' : $channel).PHP_EOL);
     }
 
+    /**
+     * @param string|null $channel
+     *
+     * @return array{path: string, version: string, min-php: int}
+     */
     public function getLatest($channel = null)
     {
         $versions = $this->getVersionsData();
@@ -79,6 +92,9 @@ class Versions
         throw new \UnexpectedValueException('There is no version of Composer available for your PHP version ('.PHP_VERSION.')');
     }
 
+    /**
+     * @return array<string, array<int, array{path: string, version: string, min-php: int}>>
+     */
     private function getVersionsData()
     {
         if (!$this->versionsData) {