diff --git a/TODO.md b/TODO.md
index 6e931f5..c4b19c5 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,5 +1,8 @@
 # Posterg TODO
 
+## Fixes
+- [x] Replace `mb_strtolower` with `strtolower` in admin/index.php (mbstring not available in php8.4-fpm)
+
 ## Features
 - [x] Student name popover preview in /repertoire (zero per-hover requests)
   - [x] `Database::getThesesByAuthorName()` query
diff --git a/app/public/admin/index.php b/app/public/admin/index.php
index f5ae99b..b073de3 100644
--- a/app/public/admin/index.php
+++ b/app/public/admin/index.php
@@ -70,7 +70,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_FILES['csv_file'])) {
                 }
 
                 // 2. Try alias map (lowercase key)
-                $key = mb_strtolower($raw, 'UTF-8');
+                $key = strtolower($raw);
                 if (isset($orientationAliases[$key])) {
                     $raw = $orientationAliases[$key];
                 }
@@ -108,7 +108,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_FILES['csv_file'])) {
                 if ($raw === '') return null;
 
                 // 1. Try alias map (lowercase key)
-                $key = mb_strtolower($raw, 'UTF-8');
+                $key = strtolower($raw);
                 if (isset($apAliases[$key])) {
                     $raw = $apAliases[$key];
                 }