diff --git a/apps/theming/lib/Controller/ThemingController.php b/apps/theming/lib/Controller/ThemingController.php
index abe9b7f48873a..227163d38f0d3 100644
--- a/apps/theming/lib/Controller/ThemingController.php
+++ b/apps/theming/lib/Controller/ThemingController.php
@@ -457,7 +457,7 @@ public function getThemeStylesheet(string $themeId, bool $plain = false, bool $w
 	#[BruteForceProtection(action: 'manifest')]
 	#[OpenAPI(scope: OpenAPI::SCOPE_DEFAULT)]
 	public function getManifest(string $app): JSONResponse {
-		$cacheBusterValue = $this->appConfig->getAppValueString('cachebuster', '0');
+		$cacheBusterValue = (string)$this->appConfig->getAppValueInt('cachebuster');
 		if ($app === 'core' || $app === 'settings') {
 			$name = $this->themingDefaults->getName();
 			$shortName = $this->themingDefaults->getName();
diff --git a/apps/theming/tests/Controller/ThemingControllerTest.php b/apps/theming/tests/Controller/ThemingControllerTest.php
index 8d1380f215cd8..0c4b81ba727e8 100644
--- a/apps/theming/tests/Controller/ThemingControllerTest.php
+++ b/apps/theming/tests/Controller/ThemingControllerTest.php
@@ -734,9 +734,9 @@ public static function dataGetManifest(): array {
 	public function testGetManifest(bool $standalone): void {
 		$this->appConfig
 			->expects($this->once())
-			->method('getAppValueString')
-			->with('cachebuster', '0')
-			->willReturn('0');
+			->method('getAppValueInt')
+			->with('cachebuster')
+			->willReturn(0);
 		$this->themingDefaults
 			->expects($this->any())
 			->method('getName')