diff --git a/homeassistant/components/mqtt/number.py b/homeassistant/components/mqtt/number.py
index 3682b19cf4e..62bb9123a76 100644
--- a/homeassistant/components/mqtt/number.py
+++ b/homeassistant/components/mqtt/number.py
@@ -12,7 +12,7 @@ from homeassistant.components.number import (
     DEFAULT_MAX_VALUE,
     DEFAULT_MIN_VALUE,
     DEFAULT_STEP,
-    DEVICE_CLASSES_SCHEMA,
+    NumberDeviceClass,
     NumberMode,
     RestoreNumber,
 )
@@ -86,7 +86,9 @@ def validate_config(config: ConfigType) -> ConfigType:
 _PLATFORM_SCHEMA_BASE = MQTT_RW_SCHEMA.extend(
     {
         vol.Optional(CONF_COMMAND_TEMPLATE): cv.template,
-        vol.Optional(CONF_DEVICE_CLASS): vol.Any(DEVICE_CLASSES_SCHEMA, None),
+        vol.Optional(CONF_DEVICE_CLASS): vol.Any(
+            vol.All(vol.Lower, vol.Coerce(NumberDeviceClass)), None
+        ),
         vol.Optional(CONF_MAX, default=DEFAULT_MAX_VALUE): vol.Coerce(float),
         vol.Optional(CONF_MIN, default=DEFAULT_MIN_VALUE): vol.Coerce(float),
         vol.Optional(CONF_MODE, default=NumberMode.AUTO): vol.Coerce(NumberMode),