@@ -544,7 +544,7 @@ def _check_bracketed_netloc(netloc):
 # Valid bracketed hosts are defined in
 # https://www.rfc-editor.org/rfc/rfc3986#page-49 and https://url.spec.whatwg.org/
 def _check_bracketed_host(hostname):
-    if hostname[0].lower() == 'v':
+    if len(hostname) > 0 and hostname[0].lower() == 'v':
         if not re.match(r"\A[vV][a-fA-F0-9]+\..+\Z", hostname):
             raise ValueError(f"IPvFuture address is invalid")
     else: