diff --git a/index.php b/index.php
index 24aad88c..290b89ec 100644
--- a/index.php
+++ b/index.php
@@ -653,6 +653,11 @@ public function verifyIntegrity() {
 			return;
 		}
 
+		if ($urlOverride) {
+			$this->silentLog('[info] custom download url provided, cannot verify signature');
+			return;
+		}
+
 		$response = $this->getUpdateServerResponse();
 		if (empty($response['signature'])) {
 			throw new \Exception('No signature specified for defined update');
diff --git a/lib/UpdateCommand.php b/lib/UpdateCommand.php
index 9a438cd9..79fbcf52 100644
--- a/lib/UpdateCommand.php
+++ b/lib/UpdateCommand.php
@@ -41,6 +41,7 @@ class UpdateCommand extends Command {
 	protected $skipBackup = false;
 
 	protected bool $skipUpgrade = false;
+	protected string $urlOverride = '';
 
 	/** @var array strings of text for stages of updater */
 	protected $checkTexts = [
@@ -65,7 +66,8 @@ protected function configure() {
 			->setDescription('Updates the code of an Nextcloud instance')
 			->setHelp("This command fetches the latest code that is announced via the updater server and safely replaces the existing code with the new one.")
 			->addOption('no-backup', null, InputOption::VALUE_NONE, 'Skip backup of current Nextcloud version')
-			->addOption('no-upgrade', null, InputOption::VALUE_NONE, "Don't automatically run occ upgrade");
+			->addOption('no-upgrade', null, InputOption::VALUE_NONE, "Don't automatically run occ upgrade")
+			->addOption('url', null, InputOption::VALUE_OPTIONAL, 'The URL of the Nextcloud release to download');
 	}
 
 	public static function getUpdaterVersion(): string {
@@ -152,7 +154,12 @@ protected function execute(InputInterface $input, OutputInterface $output) {
 		$output->writeln('Current version is ' . $this->updater->getCurrentVersion() . '.');
 
 		// needs to be called that early because otherwise updateAvailable() returns false
-		$updateString = $this->updater->checkForUpdate();
+		if ($this->urlOverride) {
+			$this->updater->log('[info] Using URL override: ' . $this->urlOverride);
+			$updateString = 'Update check forced with URL override: ' . $this->urlOverride;
+		} else {
+			$updateString = $this->updater->checkForUpdate();
+		}
 
 		$output->writeln('');
 
@@ -165,9 +172,11 @@ protected function execute(InputInterface $input, OutputInterface $output) {
 
 		$output->writeln('');
 
-		if (!$this->updater->updateAvailable() && $stepNumber === 0) {
-			$output->writeln('Nothing to do.');
-			return 0;
+		if (!$this->urlOverride) {
+			if (!$this->updater->updateAvailable() && $stepNumber === 0) {
+				$output->writeln('Nothing to do.');
+				return 0;
+			}
 		}
 
 		$questionText = 'Start update';
@@ -374,10 +383,10 @@ protected function executeStep($step) {
 					}
 					break;
 				case 4:
-					$this->updater->downloadUpdate();
+					$this->updater->downloadUpdate($this->urlOverride);
 					break;
 				case 5:
-					$this->updater->verifyIntegrity();
+					$this->updater->verifyIntegrity($this->urlOverride);
 					break;
 				case 6:
 					$this->updater->extractDownload();
diff --git a/lib/Updater.php b/lib/Updater.php
index 06f65e8b..d078c4f1 100644
--- a/lib/Updater.php
+++ b/lib/Updater.php
@@ -617,6 +617,11 @@ public function verifyIntegrity() {
 			return;
 		}
 
+		if ($urlOverride) {
+			$this->silentLog('[info] custom download url provided, cannot verify signature');
+			return;
+		}
+
 		$response = $this->getUpdateServerResponse();
 		if (empty($response['signature'])) {
 			throw new \Exception('No signature specified for defined update');
diff --git a/vendor/composer/platform_check.php b/vendor/composer/platform_check.php
index 580fa960..d2225c7d 100644
--- a/vendor/composer/platform_check.php
+++ b/vendor/composer/platform_check.php
@@ -19,8 +19,7 @@
             echo 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . str_replace('You are running '.PHP_VERSION.'.', '', implode(PHP_EOL, $issues)) . PHP_EOL.PHP_EOL;
         }
     }
-    trigger_error(
-        'Composer detected issues in your platform: ' . implode(' ', $issues),
-        E_USER_ERROR
+    throw new \RuntimeException(
+        'Composer detected issues in your platform: ' . implode(' ', $issues)
     );
 }