diff --git a/bookwyrm/views/inbox.py b/bookwyrm/views/inbox.py
index d1b75997..a8eb4851 100644
--- a/bookwyrm/views/inbox.py
+++ b/bookwyrm/views/inbox.py
@@ -70,7 +70,10 @@ def is_blocked_user_agent(request):
     user_agent = request.headers.get("User-Agent")
     if not user_agent:
         return False
-    url = re.search(r"https?://{:s}/?".format(regex.domain), user_agent).group()
+    url = re.search(r"https?://{:s}/?".format(regex.domain), user_agent)
+    if not url:
+        return False
+    url = url.group()
     return models.FederatedServer.is_blocked(url)