diff --git a/lib/private/App/AppManager.php b/lib/private/App/AppManager.php
index 8137805ac3488..655d80e9b6c91 100644
--- a/lib/private/App/AppManager.php
+++ b/lib/private/App/AppManager.php
@@ -1031,7 +1031,13 @@ public function isBackendRequired(string $backend): bool {
 	 */
 	public function cleanAppId(string $app): string {
 		/* Only lowercase alphanumeric is allowed */
-		return preg_replace('/(^[0-9_-]+|[^a-z0-9_-]+|[_-]+$)/', '', $app);
+		$cleanAppId = preg_replace('/(^[0-9_-]+|[^a-z0-9_-]+|[_-]+$)/', '', $app, -1, $count);
+		if ($count > 0) {
+			$this->logger->debug('Only lowercase alphanumeric characters are allowed in appIds; check paths of installed app [' . $count . ' characters replaced]', [
+				'app' => $cleanAppId, // safer to log $cleanAppId even if it makes more challenging to troubleshooting (part of why character count is at least logged)
+			]);
+		}
+		return $cleanAppId;
 	}
 
 	/**