diff --git a/src/Composer/InstalledVersions.php b/src/Composer/InstalledVersions.php
index c6b54af7b..153849aec 100644
--- a/src/Composer/InstalledVersions.php
+++ b/src/Composer/InstalledVersions.php
@@ -328,7 +328,9 @@ class InstalledVersions
                 if (isset(self::$installedByVendor[$vendorDir])) {
                     $installed[] = self::$installedByVendor[$vendorDir];
                 } elseif (is_file($vendorDir.'/composer/installed.php')) {
-                    $installed[] = self::$installedByVendor[$vendorDir] = require $vendorDir.'/composer/installed.php';
+                    /** @var array{root: array{name: string, pretty_version: string, version: string, reference: string|null, type: string, install_path: string, aliases: string[], dev: bool}, versions: array<string, array{pretty_version?: string, version?: string, reference?: string|null, type?: string, install_path?: string, aliases?: string[], dev_requirement: bool, replaced?: string[], provided?: string[]}>} $required */
+                    $required = require $vendorDir.'/composer/installed.php';
+                    $installed[] = self::$installedByVendor[$vendorDir] = $required;
                     if (null === self::$installed && strtr($vendorDir.'/composer', '\\', '/') === strtr(__DIR__, '\\', '/')) {
                         self::$installed = $installed[count($installed) - 1];
                     }
@@ -340,12 +342,17 @@ class InstalledVersions
             // only require the installed.php file if this file is loaded from its dumped location,
             // and not from its source location in the composer/composer package, see https://github.com/composer/composer/issues/9937
             if (substr(__DIR__, -8, 1) !== 'C') {
-                self::$installed = require __DIR__ . '/installed.php';
+                /** @var array{root: array{name: string, pretty_version: string, version: string, reference: string|null, type: string, install_path: string, aliases: string[], dev: bool}, versions: array<string, array{pretty_version?: string, version?: string, reference?: string|null, type?: string, install_path?: string, aliases?: string[], dev_requirement: bool, replaced?: string[], provided?: string[]}>} $required */
+                $required = require __DIR__ . '/installed.php';
+                self::$installed = $required;
             } else {
                 self::$installed = array();
             }
         }
-        $installed[] = self::$installed;
+
+        if (self::$installed !== array()) {
+            $installed[] = self::$installed;
+        }
 
         return $installed;
     }