diff --git a/.github/workflows/flarum-package-manager-backend.yml b/.github/workflows/flarum-package-manager-backend.yml
new file mode 100644
index 000000000..bb82c74d3
--- /dev/null
+++ b/.github/workflows/flarum-package-manager-backend.yml
@@ -0,0 +1,15 @@
+name: Package Manager PHP
+
+on: [workflow_dispatch, push, pull_request]
+
+# The reusable workflow definitions will be moved to the `flarum/framework` repo soon.
+# This will break your current script.
+# When this happens, run `flarum-cli audit infra --fix` to update your infrastructure.
+
+jobs:
+  run:
+    uses: flarum/.github/.github/workflows/REUSABLE_backend.yml@main
+    with:
+      enable_backend_testing: true
+
+      backend_directory: ./extensions/package-manager
diff --git a/extensions/package-manager/composer.json b/extensions/package-manager/composer.json
index d8e7493d0..449c0a4e7 100755
--- a/extensions/package-manager/composer.json
+++ b/extensions/package-manager/composer.json
@@ -23,7 +23,7 @@
     },
     "require": {
         "flarum/core": "^1.0.0",
-        "composer/composer": "^2.0"
+        "composer/composer": "^2.3"
     },
     "require-dev": {
         "flarum/testing": "^1.0.0",
@@ -86,7 +86,7 @@
         "test:integration": "phpunit -c tests/phpunit.integration.xml",
         "test:setup": [
             "@php tests/integration/setup.php",
-            "cd $FLARUM_TEST_TMP_DIR_LOCAL && composer install"
+            "cd ${FLARUM_TEST_TMP_DIR_LOCAL:-${FLARUM_TEST_TMP_DIR:-./tests/integration/tmp}} && composer install"
         ]
     },
     "scripts-descriptions": {
diff --git a/extensions/package-manager/src/Command/CheckForUpdatesHandler.php b/extensions/package-manager/src/Command/CheckForUpdatesHandler.php
index 2b396a0c8..8bc9a1acd 100755
--- a/extensions/package-manager/src/Command/CheckForUpdatesHandler.php
+++ b/extensions/package-manager/src/Command/CheckForUpdatesHandler.php
@@ -58,7 +58,7 @@ class CheckForUpdatesHandler
         $actor->assertAdmin();
 
         $firstOutput = $this->runComposerCommand(false);
-        $firstOutput = json_decode($firstOutput, true);
+        $firstOutput = json_decode($this->cleanJson($firstOutput), true);
 
         $majorUpdates = false;
 
@@ -71,7 +71,7 @@ class CheckForUpdatesHandler
 
         if ($majorUpdates) {
             $secondOutput = $this->runComposerCommand(true);
-            $secondOutput = json_decode($secondOutput, true);
+            $secondOutput = json_decode($this->cleanJson($secondOutput), true);
         }
 
         if (! isset($secondOutput)) {
@@ -101,6 +101,15 @@ class CheckForUpdatesHandler
             ->save();
     }
 
+    /**
+     * Composer can sometimes return text above the JSON.
+     * This method tries to remove such occurences.
+     */
+    protected function cleanJson(string $composerOutput): string
+    {
+        return preg_replace('/^[^{]+\n({.*)/ms', '$1', $composerOutput);
+    }
+
     /**
      * @throws ComposerCommandFailedException
      */
diff --git a/extensions/package-manager/tests/integration/SetupComposer.php b/extensions/package-manager/tests/integration/SetupComposer.php
index 9a1080ce4..fb021faf9 100644
--- a/extensions/package-manager/tests/integration/SetupComposer.php
+++ b/extensions/package-manager/tests/integration/SetupComposer.php
@@ -15,27 +15,11 @@ class SetupComposer
 {
     use UsesTmpDir;
 
-    private $config = [
-        'require' => [
-            'flarum/core' => '1.0.0',
-            'flarum/tags' => '1.0.3',
-            'flarum/lang-english' => '*',
-        ],
-        'config' => [
-            'preferred-install' => 'dist',
-            'sort-packages' => true,
-        ],
-        'repositories' => [
-            [
-                'type' => 'path',
-                'url' => __DIR__.'/tmp/packages/*',
-            ]
-        ]
-    ];
+    private $config;
 
     public function __construct(array $config = null)
     {
-        $this->config = array_merge($this->config, $config ?? []);
+        $this->config = $config;
     }
 
     public function run()
@@ -44,7 +28,7 @@ class SetupComposer
         $composerLock = $this->tmpDir().'/composer.lock';
         $packages = $this->tmpDir().'/packages';
 
-        file_put_contents($composerJson, json_encode($this->config, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT));
+        file_put_contents($composerJson, json_encode($this->getConfig(), JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT));
 
         if (! file_exists($packages)) {
             mkdir($packages);
@@ -53,5 +37,28 @@ class SetupComposer
         if (file_exists($composerLock)) {
             unlink($composerLock);
         }
+
+        echo 'composer.json created with testing packages directory.';
+    }
+
+    private function getConfig(): array
+    {
+        return array_merge([
+            'require' => [
+                'flarum/core' => '1.0.0',
+                'flarum/tags' => '1.0.3',
+                'flarum/lang-english' => '*',
+            ],
+            'config' => [
+                'preferred-install' => 'dist',
+                'sort-packages' => true,
+            ],
+            'repositories' => [
+                [
+                    'type' => 'path',
+                    'url' => realpath($this->tmpDir()).'/packages/*',
+                ]
+            ]
+        ], $this->config ?? []);
     }
 }
diff --git a/extensions/package-manager/tests/phpunit.integration.xml b/extensions/package-manager/tests/phpunit.integration.xml
index 2d2b64c39..89f91a4d1 100644
--- a/extensions/package-manager/tests/phpunit.integration.xml
+++ b/extensions/package-manager/tests/phpunit.integration.xml
@@ -19,10 +19,7 @@
     <testsuites>
         <testsuite name="Flarum Integration Tests">
             <directory suffix="Test.php">./integration</directory>
-             <exclude>./integration/tmp</exclude>
+            <exclude>./integration/tmp</exclude>
         </testsuite>
     </testsuites>
-    <php>
-        <env name="FLARUM_TEST_TMP_DIR_LOCAL" value="tests/integration/tmp" force="true" />
-    </php>
 </phpunit>