diff --git a/drivers/firmware/altera_serial.c b/drivers/firmware/altera_serial.c
index 232f1a6..c5ffbb6 100644
--- a/drivers/firmware/altera_serial.c
+++ b/drivers/firmware/altera_serial.c
@@ -113,7 +113,7 @@
 	u32 dummy;
 	int ret;
 
-	dev_dbg(dev, "Start writing %d bytes.\n", __func__, sz);
+	dev_dbg(dev, "Start writing %zu bytes.\n", sz);
 
 	spi_message_init(&m);