diff --git a/klippy/extras/tmc_uart.py b/klippy/extras/tmc_uart.py
index 8af0be07..c2babd9c 100644
--- a/klippy/extras/tmc_uart.py
+++ b/klippy/extras/tmc_uart.py
@@ -175,7 +175,7 @@ def lookup_tmc_uart_bitbang(config, max_addr):
     if rx_pin_params['chip'] is not tx_pin_params['chip']:
         raise ppins.error("TMC uart rx and tx pins must be on the same mcu")
     select_pins_desc = config.get('select_pins', None)
-    addr = config.getint('uart_address', 0, maxval=max_addr)
+    addr = config.getint('uart_address', 0, minval=0, maxval=max_addr)
     mcu_uart = rx_pin_params.get('class')
     if mcu_uart is None:
         mcu_uart = MCU_TMC_uart_bitbang(rx_pin_params, tx_pin_params,