diff --git a/shared-bindings/busio/UART.c b/shared-bindings/busio/UART.c
index 2d14fec07f..60f2b407fe 100644
--- a/shared-bindings/busio/UART.c
+++ b/shared-bindings/busio/UART.c
@@ -231,7 +231,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(busio_uart___exit___obj, 4, 4, busio_
 //|         ...
 //|
 
-//|     def write(self, buf: WriteableBuffer) -> Optional[int]:
+//|     def write(self, buf: ReadableBuffer) -> Optional[int]:
 //|         """Write the buffer of bytes to the bus.
 //|
 //|       *New in CircuitPython 4.0:* ``buf`` must be bytes, not a string.