diff --git a/lib/AppConfigOverwrite.php b/lib/AppConfigOverwrite.php
index da6ab2f8..1bb2ceab 100644
--- a/lib/AppConfigOverwrite.php
+++ b/lib/AppConfigOverwrite.php
@@ -30,4 +30,50 @@ public function getValue($app, $key, $default = '') {
 
 		return parent::getValue($app, $key, $default);
 	}
+
+	#[\Override]
+	public function getValueString(string $app, string $key, string $default = '', bool $lazy = false): string {
+		if (isset($this->overWrite[$app]) && isset($this->overWrite[$app][$key])) {
+			return $this->overWrite[$app][$key];
+		}
+
+		return parent::getValueString($app, $key, $default, $lazy);
+	}
+
+	#[\Override]
+	public function getValueBool(string $app, string $key, bool $default = false, bool $lazy = false): bool {
+		if (isset($this->overWrite[$app]) && isset($this->overWrite[$app][$key])) {
+			return in_array(strtolower($this->overWrite[$app][$key]), ['1', 'true', 'yes', 'on'], true);
+		}
+
+		return parent::getValueBool($app, $key, $default, $lazy);
+	}
+
+	#[\Override]
+	public function getValueInt(string $app, string $key, int $default = 0, bool $lazy = false): int {
+		if (isset($this->overWrite[$app]) && isset($this->overWrite[$app][$key])) {
+			return (int)$this->overWrite[$app][$key];
+		}
+
+		return parent::getValueInt($app, $key, $default, $lazy);
+	}
+
+	#[\Override]
+	public function getValueFloat(string $app, string $key, float $default = 0, bool $lazy = false): float {
+		if (isset($this->overWrite[$app]) && isset($this->overWrite[$app][$key])) {
+			return (float)$this->overWrite[$app][$key];
+		}
+
+		return parent::getValueFloat($app, $key, $default, $lazy);
+	}
+
+	#[\Override]
+	public function getValueArray(string $app, string $key, array $default = [], bool $lazy = false): array {
+		if (isset($this->overWrite[$app]) && isset($this->overWrite[$app][$key])) {
+			$value = json_decode($this->overWrite[$app][$key], true);
+			return is_array($value) ? $value : $default;
+		}
+
+		return parent::getValueArray($app, $key, $default, $lazy);
+	}
 }
diff --git a/tests/stub.php b/tests/stub.php
index cbddd7d4..310dd4c7 100644
--- a/tests/stub.php
+++ b/tests/stub.php
@@ -133,6 +133,21 @@ public function __construct(
 		 */
 		public function getValue($app, $key, $default = '') {
 		}
+
+		public function getValueString(string $app, string $key, string $default = '', bool $lazy = false): string {
+		}
+
+		public function getValueBool(string $app, string $key, bool $default = false, bool $lazy = false): bool {
+		}
+
+		public function getValueInt(string $app, string $key, int $default = 0, bool $lazy = false): int {
+		}
+
+		public function getValueFloat(string $app, string $key, float $default = 0, bool $lazy = false): float {
+		}
+
+		public function getValueArray(string $app, string $key, array $default = [], bool $lazy = false): array {
+		}
 	}
 }
 
diff --git a/tests/unit/AppConfigOverwriteTest.php b/tests/unit/AppConfigOverwriteTest.php
new file mode 100644
index 00000000..8f10c3a6
--- /dev/null
+++ b/tests/unit/AppConfigOverwriteTest.php
@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Guests\Test\Unit;
+
+use OCA\Guests\AppConfigOverwrite;
+use OCP\Server;
+use Test\TestCase;
+
+/**
+ * @group DB
+ */
+class AppConfigOverwriteTest extends TestCase {
+	private const KEY = 'shareapi_only_share_with_group_members';
+
+	private ?AppConfigOverwrite $appConfig = null;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->appConfig = Server::get(AppConfigOverwrite::class);
+		$this->appConfig->setOverwrite(['core' => [self::KEY => 'yes']]);
+	}
+
+	protected function tearDown(): void {
+		$this->appConfig->setOverwrite([]);
+
+		parent::tearDown();
+	}
+
+	/**
+	 * The server reads the overwritten values through several getters:
+	 * IConfig::getAppValue() ends up in getValue(), the share recipient
+	 * autocompletion uses getValueString() and OCA\Guests\Config uses
+	 * getValueBool(). All of them have to see the overwrite.
+	 */
+	public function testOverwriteIsAppliedToAllGetters(): void {
+		$this->assertSame('yes', $this->appConfig->getValue('core', self::KEY, 'no'));
+		$this->assertSame('yes', $this->appConfig->getValueString('core', self::KEY, 'no'));
+		$this->assertTrue($this->appConfig->getValueBool('core', self::KEY));
+	}
+
+	public function testWithoutOverwriteTheStoredValueIsUsed(): void {
+		$this->appConfig->setOverwrite([]);
+
+		$this->assertSame('no', $this->appConfig->getValue('core', self::KEY, 'no'));
+		$this->assertSame('no', $this->appConfig->getValueString('core', self::KEY, 'no'));
+		$this->assertFalse($this->appConfig->getValueBool('core', self::KEY));
+	}
+}