diff --git a/deluge/core/preferencesmanager.py b/deluge/core/preferencesmanager.py
index d7e301268b..802ea865cd 100644
--- a/deluge/core/preferencesmanager.py
+++ b/deluge/core/preferencesmanager.py
@@ -224,7 +224,11 @@ def __set_listen_on(self):
             interface = interface.strip()
             try:
                 # add square brackets to ipv6 only, as needed by lib torrent
-                lib_interfaces.append('['+interface+']' if ipaddress.ip_address(interface).version == 6 else interface)
+                lib_interfaces.append(
+                    '[' + interface + ']'
+                    if ipaddress.ip_address(interface).version == 6
+                    else interface
+                )
             except ValueError:
                 # ip address format failed, assume network interface name
                 lib_interfaces.append(interface)