diff --git a/custom_components/wienerlinien/sensor.py b/custom_components/wienerlinien/sensor.py
index 7ada209..2a156ec 100644
--- a/custom_components/wienerlinien/sensor.py
+++ b/custom_components/wienerlinien/sensor.py
@@ -105,7 +105,10 @@ def name(self):
     @property
     def state(self):
         """Return state."""
-        return f"{self._state[:-2]}:{self._state[26:]}"
+        if self._state is None:
+            return self._state
+        else:
+            return f"{self._state[:-2]}:{self._state[26:]}"
 
     @property
     def icon(self):