diff --git a/src/networkmonitor.py b/src/networkmonitor.py
index 0cdffaf6..cbf02913 100644
--- a/src/networkmonitor.py
+++ b/src/networkmonitor.py
@@ -166,8 +166,10 @@ def emit_state_changed(self):
     # TODO: Do this with libnm
     def same_subnet(self, other_ip_info):
         if self.current_ip_info.ip4_address is not None and other_ip_info.ip4_address is not None:
+
+            netmask = self.current_ip_info.ip4["netmask"] or self.current_ip_info.ip4["mask"]
             iface = ipaddress.IPv4Interface("%s/%s" % (self.current_ip_info.ip4_address,
-                                                    self.current_ip_info.ip4["netmask"]))
+                                                       netmask))
 
             my_net = iface.network