diff --git a/shortener/handlers.py b/shortener/handlers.py
index 64b047a..70fa2ab 100644
--- a/shortener/handlers.py
+++ b/shortener/handlers.py
@@ -1,4 +1,5 @@
 import os
+import re
 from typing import Dict
 from urllib.parse import urlparse
 
@@ -53,6 +54,12 @@ def _validate_user_input():
         raise BadRequestException(
             message="`short_code` must be longer than 4 characters."
         )
+    reg = re.compile(r"^[a-zA-Z0-9_-]+$")
+    if not reg.match(short_code):
+        raise BadRequestException(
+            message="`short_code` must only contain non accentuated letters, "
+            "digits, dashes (-) and underscores (_)."
+        )
     if _short_code_exists(short_code):
         raise BadRequestException(message=f"`{short_code}` is already taken")