diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7ab7b6f5..a3e99bd5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fix fields values updates not applying the expected checks in some cases
 - Fix ticket observers being able to edit and save additional fields they are not allowed to modify
 - Fix `Yes/No` field values returned as strings instead of integers in search results
+- Fix fatal error during plugin update caused by outdated generated dropdown classes
 
 ## [1.25.0] - 2026-10-06
 
diff --git a/hook.php b/hook.php
index 61c34778..59ef72bb 100644
--- a/hook.php
+++ b/hook.php
@@ -51,6 +51,10 @@ function plugin_fields_install()
 
     $version = $plugin_fields->fields['version'];
 
+    // Remove generated classes before migration, they may be incompatible with current GLPI version
+    // and would trigger a fatal error if autoloaded before being regenerated.
+    // They will be regenerated by `installUserData()` methods.
+    array_map(unlink(...), glob(PLUGINFIELDS_CLASS_PATH . '/*.class.php') ?: []);
 
     $migration = new Migration($version);
     if (isCommandLine()) {
diff --git a/tests/Units/InstallOutdatedGeneratedFilesTest.php b/tests/Units/InstallOutdatedGeneratedFilesTest.php
new file mode 100644
index 00000000..07c04264
--- /dev/null
+++ b/tests/Units/InstallOutdatedGeneratedFilesTest.php
@@ -0,0 +1,117 @@
+<?php
+
+/**
+ * -------------------------------------------------------------------------
+ * Fields plugin for GLPI
+ * -------------------------------------------------------------------------
+ *
+ * LICENSE
+ *
+ * This file is part of Fields.
+ *
+ * Fields is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Fields is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Fields. If not, see <http://www.gnu.org/licenses/>.
+ * -------------------------------------------------------------------------
+ * @copyright Copyright (C) 2013-2023 by Fields plugin team.
+ * @license   GPLv2 https://www.gnu.org/licenses/gpl-2.0.html
+ * @link      https://github.com/pluginsGLPI/fields
+ * -------------------------------------------------------------------------
+ */
+
+declare(strict_types=1);
+
+namespace GlpiPlugin\Field\Tests\Units;
+
+use Computer;
+use DBmysql;
+use Glpi\Tests\DbTestCase;
+use Glpi\Tests\GLPITestCase;
+use GlpiPlugin\Field\Tests\FieldTestTrait;
+use PluginFieldsContainer;
+use PluginFieldsField;
+
+require_once __DIR__ . '/../FieldTestCase.php';
+require_once __DIR__ . '/../../hook.php';
+
+final class InstallOutdatedGeneratedFilesTest extends DbTestCase
+{
+    use FieldTestTrait;
+
+    public function setUp(): void
+    {
+        GLPITestCase::setUp();
+        $this->login();
+    }
+
+    public function tearDown(): void
+    {
+        $this->tearDownFieldTest();
+        GLPITestCase::tearDown();
+    }
+
+    public function testInstallDoesNotLoadOutdatedGeneratedDropdownClass(): void
+    {
+        /** @var DBmysql $DB */
+        global $DB;
+
+        $container = $this->createFieldContainer([
+            'label'       => 'Outdated files container',
+            'type'        => 'tab',
+            'itemtypes'   => [Computer::class],
+            'is_active'   => 1,
+            'entities_id' => 0,
+        ]);
+
+        $field = $this->createField([
+            'label'                                     => 'Outdated dropdown',
+            'type'                                      => 'dropdown',
+            PluginFieldsContainer::getForeignKeyField() => $container->getID(),
+            'ranking'                                   => 1,
+            'is_active'                                 => 1,
+            'is_readonly'                               => 0,
+        ]);
+        $this->assertSame('outdateddropdownfield', $field->fields['name']);
+
+        // Simulate a dropdown generated by a previous plugin version, with a system name that does not match
+        // its label anymore (it will be renamed by the migration) and a class that has not been loaded yet.
+        $old_name             = 'notloadedyetfield';
+        $container_classname  = PluginFieldsContainer::getClassname(Computer::class, $container->fields['name']);
+        $container_table      = getTableForItemType($container_classname);
+        $container_class_file = PLUGINFIELDS_CLASS_PATH . '/' . strtolower(substr($container_classname, strlen('PluginFields'))) . '.class.php';
+        $DB->update(PluginFieldsField::getTable(), ['name' => $old_name], ['id' => $field->getID()]);
+        $DB->doQuery('RENAME TABLE `glpi_plugin_fields_outdateddropdownfielddropdowns` TO `glpi_plugin_fields_notloadedyetfielddropdowns`');
+        $DB->doQuery(
+            "ALTER TABLE `{$container_table}` CHANGE `plugin_fields_outdateddropdownfielddropdowns_id` `plugin_fields_notloadedyetfielddropdowns_id` INT UNSIGNED DEFAULT NULL",
+        );
+
+        // Outdated class file, that would trigger a fatal error if loaded (e.g. incompatible property declaration).
+        $outdated_file = PLUGINFIELDS_CLASS_PATH . '/' . $old_name . 'dropdown.class.php';
+        file_put_contents($outdated_file, '<?php throw new \RuntimeException("Outdated generated class has been loaded.");');
+        $this->assertFileExists($container_class_file);
+
+        ob_start();
+        $result = plugin_fields_install();
+        ob_end_clean();
+        $DB->clearSchemaCache();
+
+        $this->assertTrue($result);
+
+        // Outdated file has been removed, dropdown has been renamed and its files regenerated
+        $this->assertFileDoesNotExist($outdated_file);
+        $this->assertTrue($field->getFromDB($field->getID()));
+        $this->assertSame('outdateddropdownfield', $field->fields['name']);
+        $this->assertTrue($DB->tableExists('glpi_plugin_fields_outdateddropdownfielddropdowns'));
+        $this->assertFileExists(PLUGINFIELDS_CLASS_PATH . '/outdateddropdownfielddropdown.class.php');
+        $this->assertFileExists($container_class_file);
+    }
+}