diff --git a/WebHostLib/upload.py b/WebHostLib/upload.py
index 89a839cf..e7ac0339 100644
--- a/WebHostLib/upload.py
+++ b/WebHostLib/upload.py
@@ -104,13 +104,21 @@ def upload_zip_to_db(zfile: zipfile.ZipFile, owner=None, meta={"race": False}, s
 
         # Factorio
         elif file.filename.endswith(".zip"):
-            _, _, slot_id, *_ = file.filename.split('_')[0].split('-', 3)
+            try:
+                _, _, slot_id, *_ = file.filename.split('_')[0].split('-', 3)
+            except ValueError:
+                flash("Error: Unexpected file found in .zip: " + file.filename)
+                return
             data = zfile.open(file, "r").read()
             files[int(slot_id[1:])] = data
 
         # All other files using the standard MultiWorld.get_out_file_name_base method
         else:
-            _, _, slot_id, *_ = file.filename.split('.')[0].split('_', 3)
+            try:
+                _, _, slot_id, *_ = file.filename.split('.')[0].split('_', 3)
+            except ValueError:
+                flash("Error: Unexpected file found in .zip: " + file.filename)
+                return
             data = zfile.open(file, "r").read()
             files[int(slot_id[1:])] = data