diff --git a/app/Http/Controllers/Admin/ReleaseController.php b/app/Http/Controllers/Admin/ReleaseController.php
index a68ff65..2d2b5e2 100644
--- a/app/Http/Controllers/Admin/ReleaseController.php
+++ b/app/Http/Controllers/Admin/ReleaseController.php
@@ -68,7 +68,17 @@ final class ReleaseController extends Controller
             'version' => ['required','string','max:40'], 'build_number' => ['required','integer','min:1'],
             'channel' => ['required', Rule::in(['stable','beta'])], 'minimum_macos' => ['nullable','string','max:30'],
             'release_notes' => ['nullable','string','max:20000'], 'sparkle_signature' => ['nullable','string','max:2000'],
-            'package' => [$release->exists ? 'nullable' : 'required','file','max:1048576','mimes:dmg,zip'],
+            'package' => [
+                $release->exists ? 'nullable' : 'required',
+                'file',
+                'max:1048576',
+                function (string $attribute, $value, \Closure $fail): void {
+                    $extension = strtolower($value->getClientOriginalExtension());
+                    if (! in_array($extension, ['dmg', 'zip'], true)) {
+                        $fail('The package must be a DMG or ZIP file.');
+                    }
+                },
+            ],
             'is_published' => ['nullable','boolean'], 'is_featured' => ['nullable','boolean'],
         ]);
         $data['is_published'] = $request->boolean('is_published');