diff --git a/extensions/package-manager/src/Command/MajorUpdateHandler.php b/extensions/package-manager/src/Command/MajorUpdateHandler.php
index a1dd5d89f..7c9f1da2b 100644
--- a/extensions/package-manager/src/Command/MajorUpdateHandler.php
+++ b/extensions/package-manager/src/Command/MajorUpdateHandler.php
@@ -9,10 +9,9 @@
 
 namespace Flarum\PackageManager\Command;
 
-use Flarum\Foundation\Paths;
 use Flarum\PackageManager\Composer\ComposerAdapter;
+use Flarum\PackageManager\Composer\ComposerJson;
 use Illuminate\Contracts\Events\Dispatcher;
-use Illuminate\Support\Arr;
 use Flarum\PackageManager\Event\FlarumUpdated;
 use Flarum\PackageManager\Exception\ComposerUpdateFailedException;
 use Flarum\PackageManager\LastUpdateCheck;
@@ -36,21 +35,22 @@ class MajorUpdateHandler
     protected $events;
 
     /**
-     * @var Paths
-     */
-    protected $paths;
-
-    /**
-     * @var array
+     * @var ComposerJson
      */
     protected $composerJson;
 
-    public function __construct(ComposerAdapter $composer, LastUpdateCheck $lastUpdateCheck, Dispatcher $events, Paths $paths)
+    /**
+     * @param ComposerAdapter $composer
+     * @param LastUpdateCheck $lastUpdateCheck
+     * @param Dispatcher $events
+     * @param ComposerJson $composerJson
+     */
+    public function __construct(ComposerAdapter $composer, LastUpdateCheck $lastUpdateCheck, Dispatcher $events, ComposerJson $composerJson)
     {
         $this->composer = $composer;
         $this->lastUpdateCheck = $lastUpdateCheck;
         $this->events = $events;
-        $this->paths = $paths;
+        $this->composerJson = $composerJson;
     }
 
     /**
@@ -67,7 +67,7 @@ class MajorUpdateHandler
     {
         $command->actor->assertAdmin();
 
-        $majorVersion = $this->getNewMajorVersion();
+        $majorVersion = $this->lastUpdateCheck->getNewMajorVersion();
 
         if (! $majorVersion) {
             return false;
@@ -78,7 +78,7 @@ class MajorUpdateHandler
         $this->runCommand($command->dryRun);
 
         if ($command->dryRun) {
-            $this->revertComposerJson();
+            $this->composerJson->revert();
 
             return true;
         }
@@ -92,36 +92,10 @@ class MajorUpdateHandler
         return true;
     }
 
-    protected function getNewMajorVersion(): ?string
-    {
-        $core = Arr::first($this->lastUpdateCheck->get()['updates']['installed'], function ($package) {
-            return $package['name'] === 'flarum/core';
-        });
-
-        return $core ? $core['latest-major'] : null;
-    }
-
     protected function updateComposerJson(string $majorVersion): void
     {
-        $composerJsonPath = $this->paths->base . '/composer.json';
-        $this->composerJson = $newComposerJson = json_decode(file_get_contents($composerJsonPath), true);
-
-        foreach ($newComposerJson['require'] as $name => &$version) {
-            if ($name === 'flarum/core') {
-                $version = '^'.str_replace('v', '', $majorVersion);
-            } else {
-                $version = '*';
-            }
-        }
-
-        file_put_contents($composerJsonPath, json_encode($newComposerJson));
-    }
-
-    protected function revertComposerJson(): void
-    {
-        $composerJsonPath = $this->paths->base . '/composer.json';
-        // @todo use filesystem for all file_get_contents
-        file_put_contents($composerJsonPath, $this->composerJson);
+        $this->composerJson->require('*', '*');
+        $this->composerJson->require('flarum/core', '^'.str_replace('v', '', $majorVersion));
     }
 
     /**
diff --git a/extensions/package-manager/src/Composer/ComposerJson.php b/extensions/package-manager/src/Composer/ComposerJson.php
new file mode 100644
index 000000000..e0a56c020
--- /dev/null
+++ b/extensions/package-manager/src/Composer/ComposerJson.php
@@ -0,0 +1,83 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\PackageManager\Composer;
+
+use Flarum\Foundation\Paths;
+use Illuminate\Filesystem\Filesystem;
+
+class ComposerJson
+{
+    /**
+     * @var Paths
+     */
+    protected $paths;
+
+    /**
+     * @var Filesystem
+     */
+    protected $filesystem;
+
+    /**
+     * @var array
+     */
+    protected $initialJson;
+
+    public function __construct(Paths $paths, Filesystem $filesystem)
+    {
+        $this->paths = $paths;
+        $this->filesystem = $filesystem;
+    }
+
+    public function require(string $packageName, string $version): void
+    {
+        $composerJson = $this->getComposerJson();
+
+        if (strpos($packageName, '*') === false) {
+            $composerJson['require'][$packageName] = $version;
+        } else {
+            foreach ($composerJson['require'] as $p => $v) {
+                if (preg_match(preg_quote(str_replace('*', '.*', $packageName), '/'), $p, $matches)) {
+                    $composerJson['require'][$p] = $version;
+                }
+            }
+        }
+
+        $this->setComposerJson($composerJson);
+    }
+
+    public function revert(): void
+    {
+        $this->setComposerJson($this->initialJson);
+    }
+
+    protected function getComposerJsonPath(): string
+    {
+        return $this->paths->base . '/composer.json';
+    }
+
+    /**
+     * @throws \Illuminate\Contracts\Filesystem\FileNotFoundException
+     */
+    protected function getComposerJson(): array
+    {
+        $json = json_decode($this->filesystem->get($this->getComposerJsonPath()), true);
+
+        if (! $this->initialJson) {
+            $this->initialJson = $json;
+        }
+
+        return $json;
+    }
+
+    protected function setComposerJson(array $json): void
+    {
+        $this->filesystem->put($this->getComposerJsonPath(), json_encode($json, JSON_PRETTY_PRINT));
+    }
+}
diff --git a/extensions/package-manager/src/Exception/ComposerCommandFailedException.php b/extensions/package-manager/src/Exception/ComposerCommandFailedException.php
index 601ac859b..42c65502f 100755
--- a/extensions/package-manager/src/Exception/ComposerCommandFailedException.php
+++ b/extensions/package-manager/src/Exception/ComposerCommandFailedException.php
@@ -27,7 +27,7 @@ class ComposerCommandFailedException extends Exception
 
     public function guessCause(): ?string
     {
-
+        return null;
     }
 
     protected function getRawPackageName(): string
diff --git a/extensions/package-manager/src/LastUpdateCheck.php b/extensions/package-manager/src/LastUpdateCheck.php
index aa93d2f42..8466c2f62 100755
--- a/extensions/package-manager/src/LastUpdateCheck.php
+++ b/extensions/package-manager/src/LastUpdateCheck.php
@@ -11,6 +11,7 @@ namespace Flarum\PackageManager;
 
 use Carbon\Carbon;
 use Flarum\Settings\SettingsRepositoryInterface;
+use Illuminate\Support\Arr;
 use Illuminate\Support\Str;
 
 class LastUpdateCheck
@@ -44,6 +45,15 @@ class LastUpdateCheck
         return json_decode($this->settings->get(self::KEY, '{}'), true);
     }
 
+    public function getNewMajorVersion(): ?string
+    {
+        $core = Arr::first($this->get()['updates']['installed'], function ($package) {
+            return $package['name'] === 'flarum/core';
+        });
+
+        return $core ? $core['latest-major'] : null;
+    }
+
     public function forget(string $name, bool $wildcard = false): void
     {
         $lastUpdateCheck = json_decode($this->settings->get(self::KEY, '{}'), true);