diff --git a/custom_components/versatile_thermostat/config_schema.py b/custom_components/versatile_thermostat/config_schema.py
index bcb21cf..1c35830 100644
--- a/custom_components/versatile_thermostat/config_schema.py
+++ b/custom_components/versatile_thermostat/config_schema.py
@@ -232,7 +232,7 @@ STEP_TPI_DATA_SCHEMA = vol.Schema(  # pylint: disable=invalid-name
 STEP_CENTRAL_TPI_DATA_SCHEMA = vol.Schema(  # pylint: disable=invalid-name
     {
         vol.Required(CONF_TPI_COEF_INT, default=0.6): selector.NumberSelector(selector.NumberSelectorConfig(min=0.0, max=1.0, step=0.01, mode=selector.NumberSelectorMode.BOX)),
-        vol.Required(CONF_TPI_COEF_EXT, default=0.01): selector.NumberSelector(selector.NumberSelectorConfig(min=0.0, max=1.0, mode=selector.NumberSelectorMode.BOX)),
+        vol.Required(CONF_TPI_COEF_EXT, default=0.01): selector.NumberSelector(selector.NumberSelectorConfig(min=0.0, max=1.0, step=0.001, mode=selector.NumberSelectorMode.BOX)),
     }
 )