diff --git a/homeassistant/components/nest/climate_sdm.py b/homeassistant/components/nest/climate_sdm.py
index fbaeb502b42..368eb8b3465 100644
--- a/homeassistant/components/nest/climate_sdm.py
+++ b/homeassistant/components/nest/climate_sdm.py
@@ -318,6 +318,6 @@ class ThermostatEntity(ClimateEntity):
     async def async_set_fan_mode(self, fan_mode):
         """Set new target fan mode."""
         if fan_mode not in self.fan_modes:
-            raise ValueError(f"Unsupported fan__mode '{fan_mode}'")
+            raise ValueError(f"Unsupported fan_mode '{fan_mode}'")
         trait = self._device.traits[FanTrait.NAME]
         await trait.set_timer(FAN_INV_MODE_MAP[fan_mode])