diff --git a/server/src/unshorteners.py b/server/src/unshorteners.py
index dea5a6a..942884a 100644
--- a/server/src/unshorteners.py
+++ b/server/src/unshorteners.py
@@ -3,7 +3,7 @@ import re
 import requests
 
 
-def unshorten_twitter(url):
+def unshorten_twitter(url: str):
     """Retrieve the actual URL behind a Twitter URL."""
     pattern = re.compile(r"<title>(.*?)<\/title>")