diff --git a/app/routers/maps.py b/app/routers/maps.py
index 8217db6..9e3b7db 100644
--- a/app/routers/maps.py
+++ b/app/routers/maps.py
@@ -3,6 +3,7 @@ import io
 import os.path
 import pathlib
 import zipfile
+import binascii
 from typing import List, Optional
 from fastapi import APIRouter, HTTPException, Query
 from ..schemas import *
@@ -42,34 +43,39 @@ async def get_map_by_crc(human_crc: Optional[str] = Query(None, min_length=8, ma
 
 @router.post("/maps", tags=["maps"], response_model=MapOut)
 async def upload_map(map_in: MapIn):
-    allowed_name = re.compile("[a-zA-Z-_.\d\(\)\[\] ]+.gck")
+    allowed_name = re.compile(r"[a-zA-Z-_.\d()\[\] ]+.gck")
     filename = map_in.name
     if not allowed_name.fullmatch(filename):
         raise HTTPException(status_code=400, detail="Invalid filename")
 
-    map_bytes = base64.b64decode(map_in.b64_data.encode("utf8"))
-    if len(map_bytes) > MAX_UPLOAD_SIZE:
+    try:
+        map_bytes = base64.b64decode(map_in.b64_data.encode("utf8"))
+    except binascii.Error:
+        raise HTTPException(status_code=400, detail="Invalid base64 data")
+
+    if len(map_in.b64_data) > MAX_UPLOAD_SIZE:
         raise HTTPException(status_code=400, detail="File too big")
 
+    crc = crc32(map_bytes)
+    for existing_map in MAPS:
+        if existing_map["crc"] == crc:
+            return MapOut(**existing_map)
+
     map_io = io.BytesIO(map_bytes)
     try:
         zipfile.ZipFile(map_io)
     except zipfile.BadZipfile:
         raise HTTPException(status_code=400, detail="File is not a valid map")
 
-    crc = crc32(map_bytes)
-    existing_map = [gmap for gmap in MAPS if gmap["crc"] == crc]
-    if existing_map:
-        return MapOut(**existing_map[0])
-    else:
-        uploaded_filename = filename
-        i = 0
-        while os.path.exists(f"{config['upload_path']}{uploaded_filename}"):
-            file_wo_ext = ".".join(filename.split('.')[0:-1])
-            uploaded_filename = f"{file_wo_ext}-{i}.gck"
-            i += 1
-        with open(f"{config['upload_path']}{uploaded_filename}", "wb") as fp:
-            fp.write(map_bytes)
-        gmap = map_file_to_dict(pathlib.Path(f"{config['upload_path']}{uploaded_filename}"))
-        MAPS.append(gmap)
-        return MapOut(**gmap)
+    # upload that map
+    uploaded_filename = filename
+    i = 0
+    while os.path.exists(f"{config['upload_path']}{uploaded_filename}"):
+        file_wo_ext = ".".join(filename.split('.')[0:-1])
+        uploaded_filename = f"{file_wo_ext}-{i}.gck"
+        i += 1
+    with open(f"{config['upload_path']}{uploaded_filename}", "wb") as fp:
+        fp.write(map_bytes)
+    gmap = map_file_to_dict(pathlib.Path(f"{config['upload_path']}{uploaded_filename}"))
+    MAPS.append(gmap)
+    return MapOut(**gmap)