diff --git a/api/src/models/container.model.ts b/api/src/models/container.model.ts
index 202b6ab..732ec23 100644
--- a/api/src/models/container.model.ts
+++ b/api/src/models/container.model.ts
@@ -19,7 +19,7 @@ import { Page } from '.';
 @Table({
     paranoid: true
 })
-export default class Container extends Model<Container> {
+export default class Container extends Model {
     @PrimaryKey
     @AutoIncrement
     @Column(DataType.INTEGER)
@@ -73,7 +73,7 @@ export default class Container extends Model<Container> {
 
             page.changed('updatedAt', true);
 
-            return await page.save();
+            await page.save().then(() => {});
         });
     }
 }
diff --git a/api/src/models/page.model.ts b/api/src/models/page.model.ts
index bcda96f..6b2db64 100644
--- a/api/src/models/page.model.ts
+++ b/api/src/models/page.model.ts
@@ -19,7 +19,7 @@ import { Container } from '.';
 @Table({
     paranoid: true
 })
-export default class Page extends Model<Page> {
+export default class Page extends Model {
     @PrimaryKey
     @Column(DataType.TEXT)
     public slug: string;
diff --git a/api/src/utils/UploadService.ts b/api/src/utils/UploadService.ts
index ba91d25..8b7729e 100644
--- a/api/src/utils/UploadService.ts
+++ b/api/src/utils/UploadService.ts
@@ -33,9 +33,9 @@ export class UploadService {
     }
 
     public saveFile (buffer: Buffer, mimeType: string): string {
-        if (!UploadService.MINE_TYPES.has(mimeType.toLowerCase())) throw new Error(`MIME type '${mimeType}' is not allowed`);
+        const fileEnding = UploadService.MINE_TYPES.get(mimeType.toLowerCase());
 
-        const fileEnding: string = UploadService.MINE_TYPES.get(mimeType.toLowerCase());
+        if (fileEnding === undefined) throw new Error(`MIME type '${mimeType}' is not allowed`);
 
         // generate random name
         let name = UploadService.randomName();
diff --git a/api/src/utils/sitemap.ts b/api/src/utils/sitemap.ts
index c12f37a..d7eb8c1 100644
--- a/api/src/utils/sitemap.ts
+++ b/api/src/utils/sitemap.ts
@@ -3,7 +3,7 @@ import { SitemapStream, streamToPromise } from 'sitemap';
 import { createGzip } from 'zlib';
 import { Page } from '../models';
 
-let cachedSitemap: Buffer | null = null;
+let cachedSitemap: Buffer;
 
 const BUILD_TIME_PATH = '/build-date.txt';
 let buildTime = new Date(0);
diff --git a/api/src/v1/routes/upload.router.ts b/api/src/v1/routes/upload.router.ts
index c56a6f1..952f6cd 100644
--- a/api/src/v1/routes/upload.router.ts
+++ b/api/src/v1/routes/upload.router.ts
@@ -15,7 +15,7 @@ uploadRouter.post('/', [
 ], wrapAsync(async (req, res) => {
     res.setHeader('Accept', UploadService.ALLOWED_MIME_TYPES.join(', '));
 
-    const contentTypeHeader = req.get('Content-Type');
+    const contentTypeHeader = req.get('Content-Type') ?? '';
     const mime = contentTypeHeader.toLowerCase();
 
     if (!UploadService.ALLOWED_MIME_TYPES.includes(mime)) {