diff --git a/homeassistant/components/sensor/uk_transport.py b/homeassistant/components/sensor/uk_transport.py
index b9ce98ec257..bcac4b47279 100644
--- a/homeassistant/components/sensor/uk_transport.py
+++ b/homeassistant/components/sensor/uk_transport.py
@@ -180,9 +180,12 @@ class UkTransportLiveBusTimeSensor(UkTransportSensor):
                             'estimated': departure['best_departure_estimate']
                         })
 
-            self._state = min(map(
-                _delta_mins, [bus['scheduled'] for bus in self._next_buses]
-            ))
+            if self._next_buses:
+                self._state = min(
+                    _delta_mins(bus['scheduled'])
+                    for bus in self._next_buses)
+            else:
+                self._state = None
 
     @property
     def device_state_attributes(self):
@@ -242,10 +245,12 @@ class UkTransportLiveTrainTimeSensor(UkTransportSensor):
                         'operator_name': departure['operator_name']
                         })
 
-                self._state = min(map(
-                    _delta_mins,
-                    [train['scheduled'] for train in self._next_trains]
-                ))
+                if self._next_trains:
+                    self._state = min(
+                        _delta_mins(train['scheduled'])
+                        for train in self._next_trains)
+                else:
+                    self._state = None
 
     @property
     def device_state_attributes(self):