diff --git a/src/calibre/gui2/actions/device.py b/src/calibre/gui2/actions/device.py
index 2921b1d8e2..9779e05cad 100644
--- a/src/calibre/gui2/actions/device.py
+++ b/src/calibre/gui2/actions/device.py
@@ -23,6 +23,8 @@ def local_url_for_content_server():
     protocol = 'https' if opts.ssl_certfile and opts.ssl_keyfile else 'http'
     prefix = opts.url_prefix or ''
     port = opts.port
+    if ':' in interface:
+        interface = f'[{interface}]'
     return f'{protocol}://{interface}:{port}{prefix}'