diff --git a/homeassistant/components/thermostat/heat_control.py b/homeassistant/components/thermostat/heat_control.py
index b87ca327b550ea440872da5fb221bc1670e4b1f7..bfec48fea3d0814ca7cf6d92b95d58463a257f8a 100644
--- a/homeassistant/components/thermostat/heat_control.py
+++ b/homeassistant/components/thermostat/heat_control.py
@@ -150,4 +150,5 @@ class HeatControl(ThermostatDevice):
 
     @property
     def _is_heating(self):
+        """ If the heater is currently heating. """
         return switch.is_on(self.hass, self.heater_entity_id)