diff --git a/custom_components/sat/mqtt/__init__.py b/custom_components/sat/mqtt/__init__.py
index fc5eb524..65567825 100644
--- a/custom_components/sat/mqtt/__init__.py
+++ b/custom_components/sat/mqtt/__init__.py
@@ -196,7 +196,7 @@ async def async_set_heater_state(self, state: DeviceState) -> None:
         await super().async_set_heater_state(state)
 
     async def async_control_max_relative_mod(self, value: float) -> None:
-        await self._send_command("MM={value}")
+        await self._send_command(f"MM={value}")
 
         await super().async_set_control_max_relative_modulation(value)