diff --git a/boot/zephyr/serial_adapter.c b/boot/zephyr/serial_adapter.c
index 896ed52..8787780 100644
--- a/boot/zephyr/serial_adapter.c
+++ b/boot/zephyr/serial_adapter.c
@@ -115,7 +115,7 @@
 }
 
 static void
-boot_uart_fifo_callback(struct device *dev)
+boot_uart_fifo_callback(struct device *dev, void *user_data)
 {
 	static struct line_input *cmd;
 	uint8_t byte;