diff --git a/custom_components/versatile_thermostat/climate.py b/custom_components/versatile_thermostat/climate.py
index 4a0a6e0..4fbf7b6 100644
--- a/custom_components/versatile_thermostat/climate.py
+++ b/custom_components/versatile_thermostat/climate.py
@@ -454,11 +454,13 @@ def post_init(self, entry_infos):
         self._security_delay_min = entry_infos.get(CONF_SECURITY_DELAY_MIN)
         self._security_min_on_percent = (
             entry_infos.get(CONF_SECURITY_MIN_ON_PERCENT)
-            or DEFAULT_SECURITY_MIN_ON_PERCENT
+            if entry_infos.get(CONF_SECURITY_MIN_ON_PERCENT) is not None
+            else DEFAULT_SECURITY_MIN_ON_PERCENT
         )
         self._security_default_on_percent = (
             entry_infos.get(CONF_SECURITY_DEFAULT_ON_PERCENT)
-            or DEFAULT_SECURITY_DEFAULT_ON_PERCENT
+            if entry_infos.get(CONF_SECURITY_DEFAULT_ON_PERCENT) is not None
+            else DEFAULT_SECURITY_DEFAULT_ON_PERCENT
         )
         self._minimal_activation_delay = entry_infos.get(CONF_MINIMAL_ACTIVATION_DELAY)
         self._last_temperature_mesure = datetime.now(tz=self._current_tz)
diff --git a/custom_components/versatile_thermostat/tests/test_bugs.py b/custom_components/versatile_thermostat/tests/test_bugs.py
index d8f55c8..013809e 100644
--- a/custom_components/versatile_thermostat/tests/test_bugs.py
+++ b/custom_components/versatile_thermostat/tests/test_bugs.py
@@ -82,3 +82,50 @@ async def test_bug_56(
 
         # Should not failed
         entity.update_custom_attributes()
+
+
+async def test_bug_63(
+    hass: HomeAssistant,
+    skip_hass_states_is_state,
+    skip_turn_on_off_heater,
+    skip_send_event,
+):
+    """Test that it should be possible to set the security_default_on_percent to 0"""
+
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        title="TheOverSwitchMockName",
+        unique_id="uniqueId",
+        data={
+            CONF_NAME: "TheOverSwitchMockName",
+            CONF_THERMOSTAT_TYPE: CONF_THERMOSTAT_SWITCH,
+            CONF_TEMP_SENSOR: "sensor.mock_temp_sensor",
+            CONF_EXTERNAL_TEMP_SENSOR: "sensor.mock_ext_temp_sensor",
+            CONF_CYCLE_MIN: 5,
+            CONF_TEMP_MIN: 15,
+            CONF_TEMP_MAX: 30,
+            "eco_temp": 17,
+            "comfort_temp": 18,
+            "boost_temp": 19,
+            CONF_USE_WINDOW_FEATURE: False,
+            CONF_USE_MOTION_FEATURE: False,
+            CONF_USE_POWER_FEATURE: False,
+            CONF_USE_PRESENCE_FEATURE: False,
+            CONF_HEATER: "switch.mock_switch",
+            CONF_PROP_FUNCTION: PROPORTIONAL_FUNCTION_TPI,
+            CONF_TPI_COEF_INT: 0.3,
+            CONF_TPI_COEF_EXT: 0.01,
+            CONF_MINIMAL_ACTIVATION_DELAY: 30,
+            CONF_SECURITY_DELAY_MIN: 5,
+            CONF_SECURITY_MIN_ON_PERCENT: 0.5,
+            CONF_SECURITY_DEFAULT_ON_PERCENT: 0.0,  # !! here
+            CONF_DEVICE_POWER: 200,
+        },
+    )
+
+    entity: VersatileThermostat = await create_thermostat(
+        hass, entry, "climate.theoverswitchmockname"
+    )
+    assert entity
+
+    assert entity._security_default_on_percent == 0