diff --git a/esphome/components/modbus_controller/__init__.py b/esphome/components/modbus_controller/__init__.py
index 1c23783ce3..c45c338bb3 100644
--- a/esphome/components/modbus_controller/__init__.py
+++ b/esphome/components/modbus_controller/__init__.py
@@ -279,7 +279,7 @@ def modbus_calc_properties(config):
             if isinstance(value, str):
                 value = value.encode()
             config[CONF_ADDRESS] = binascii.crc_hqx(value, 0)
-        config[CONF_REGISTER_TYPE] = ModbusRegisterType.CUSTOM
+        config[CONF_REGISTER_TYPE] = cv.enum(MODBUS_REGISTER_TYPE)("custom")
         config[CONF_FORCE_NEW_RANGE] = True
     return byte_offset, reg_count