diff --git a/lib/imageserv.js b/lib/imageserv.js
index fdf38f42..3215f3af 100644
--- a/lib/imageserv.js
+++ b/lib/imageserv.js
@@ -29,7 +29,7 @@ const storage = multer.diskStorage({ // multers disk storage settings
 const upload = multer({
     storage,
     fileFilter(req, file, cb) {
-        const extension = path.extname(file.originalname);
+        const extension = path.extname(file.originalname).toLowerCase();
         if (!allowedExtensions.includes(extension)) {
             const allowed = allowedExtensions.map((e) => `'${e}'`).join(', ');
             return cb(new Error(`Allowed extensions: ${allowed}, but '${extension}' was passed.`));
@@ -65,7 +65,7 @@ exports.uploadImage = async (req, res) => {
     const buffer = readChunk.sync(req.file.path, 0, 4100);
     const type = await FileType.fromBuffer(buffer);
 
-    const originalExtension = path.extname(req.file.originalname);
+    const originalExtension = path.extname(req.file.originalname).toLowerCase();
     const determinedExtension = (type && type.ext ? `.${type.ext}` : 'unknown');
 
     if (originalExtension !== determinedExtension || !allowedExtensions.includes(determinedExtension)) {
diff --git a/test/api/file-upload.test.js b/test/api/file-upload.test.js
index 9f2a4866..27d0b65a 100644
--- a/test/api/file-upload.test.js
+++ b/test/api/file-upload.test.js
@@ -113,6 +113,26 @@ describe('File upload', () => {
         expect(fs.existsSync(imgPath)).toEqual(true);
     });
 
+    it('should upload a file if it\'s valid, but has extension in capital letters', async () => {
+        const res = await request({
+            uri: '/single/' + event.id + '/upload',
+            method: 'POST',
+            headers: { 'X-Auth-Token': 'blablabla' },
+            formData: {
+                head_image: fs.createReadStream('./test/assets/valid_second_image.PNG')
+            }
+        });
+
+        expect(res.statusCode).toEqual(200);
+        expect(res.body.success).toEqual(true);
+        expect(res.body).toHaveProperty('message');
+
+        const eventFromDb = await Event.findByPk(event.id);
+
+        const imgPath = path.join(__dirname, '..', '..', config.media_dir, 'headimages', eventFromDb.image);
+        expect(fs.existsSync(imgPath)).toEqual(true);
+    });
+
     it('should remove the old file', async () => {
         // Uploading
         const firstRequest = await request({
diff --git a/test/assets/valid_second_image.PNG b/test/assets/valid_second_image.PNG
new file mode 100644
index 00000000..cff2bd3e
Binary files /dev/null and b/test/assets/valid_second_image.PNG differ