diff --git a/core/Controller/CssController.php b/core/Controller/CssController.php
index 323dd21496..a8d182418d 100644
--- a/core/Controller/CssController.php
+++ b/core/Controller/CssController.php
@@ -59,7 +59,7 @@ class CssController extends Controller {
 	 *
 	 * @param string $fileName css filename with extension
 	 * @param string $appName css folder name
-	 * @return text/css
+	 * @return FileDisplayResponse|NotFoundResponse
 	 */
 	public function getCss($fileName, $appName) {
 		try {
diff --git a/lib/private/CssManager.php b/lib/private/CssManager.php
index 8ab9a778b1..ba5ce0dd2b 100644
--- a/lib/private/CssManager.php
+++ b/lib/private/CssManager.php
@@ -23,6 +23,7 @@ namespace OC;
 
 use OCP\Files\IAppData;
 use OCP\Files\NotFoundException;
+use OCP\Files\SimpleFS\ISimpleFile;
 use OCP\ICssManager;
 
 /**
@@ -53,15 +54,7 @@ class CssManager implements ICssManager {
 	 * @throws NotFoundException
 	 */
 	public function getCss($fileName, $appName) {
-		try {
-			$folder = $this->appData->getFolder($appName);
-		} catch(NotFoundException $e) {
-			throw new NotFoundException();
-		}
-		try {
-			return $folder->getFile($fileName);
-		} catch(NotFoundException $e) {
-			throw new NotFoundException();
-		}
+		$folder = $this->appData->getFolder($appName);
+		return $folder->getFile($fileName);
 	}
 }
diff --git a/lib/private/Server.php b/lib/private/Server.php
index 381ac3fa98..b3449f14c3 100644
--- a/lib/private/Server.php
+++ b/lib/private/Server.php
@@ -417,7 +417,7 @@ class Server extends ServerContainer implements IServerContainer {
 				$c->getConfig()
 			);
 		});
-		$this->registerService('CssManager', function (Server $c) {
+		$this->registerService(CssManager::class, function (Server $c) {
 			return new CssManager(
 				$c->getAppDataDir('css')
 			);
@@ -918,7 +918,7 @@ class Server extends ServerContainer implements IServerContainer {
 	 * @return \OCP\ICssManager
 	 */
 	public function getCssManager() {
-		return $this->query('CssManager');
+		return $this->query(CssManager::class);
 	}
 
 	/**
diff --git a/lib/private/Template/SCSSCacher.php b/lib/private/Template/SCSSCacher.php
index 0b22e44d7c..db08653c88 100755
--- a/lib/private/Template/SCSSCacher.php
+++ b/lib/private/Template/SCSSCacher.php
@@ -23,8 +23,8 @@ namespace OC\Template;
 
 use Leafo\ScssPhp\Compiler;
 use Leafo\ScssPhp\Exception\ParserException;
+use OC\Files\SimpleFS\SimpleFolder;
 use OCP\Files\NotFoundException;
-use OCP\IURLGenerator;
 
 class SCSSCacher {
 
@@ -35,7 +35,7 @@ class SCSSCacher {
 	 * @var string The css filename with extension
 	 * @var string Absolute path to scss file location folder
 	 * @var string Path to scss file from the root installation
-	 * @var OC\Files\SimpleFS\SimpleFolder The folder we're putting our compiled css files
+	 * @var SimpleFolder The folder we're putting our compiled css files
 	 */
 	protected $root, $file, $fileNameSCSS, $fileNameCSS, $fileLoc, $rootCssLoc, $folder;
 
@@ -150,7 +150,6 @@ class SCSSCacher {
 		} catch(NotFoundException $e) {
 			return false;
 		}
-		return false;
 	}
 
 	/**
diff --git a/lib/public/ICssManager.php b/lib/public/ICssManager.php
index 776ffefd82..3880150297 100644
--- a/lib/public/ICssManager.php
+++ b/lib/public/ICssManager.php
@@ -21,6 +21,9 @@
 
 namespace OCP;
 
+use OCP\Files\NotFoundException;
+use OCP\Files\SimpleFS\ISimpleFile;
+
 /**
  * This class provides scss functionality
  * @since 11.0.0
@@ -34,6 +37,7 @@ interface ICssManager {
 	 * @param string $fileName css filename with extension
 	 * @param string $appName css app name
 	 * @return ISimpleFile
+	 * @throws NotFoundException
 	 */
 	public function getCss($fileName, $appName);
 }