diff --git a/firmware/drivers/serial.c b/firmware/drivers/serial.c
index 039f7913a0..a789f880fc 100644
--- a/firmware/drivers/serial.c
+++ b/firmware/drivers/serial.c
@@ -88,6 +88,7 @@ int rx_rdy(void)
 void tx_writec(unsigned char c)
 {
     /* a dummy */
+    (void)c;
 }
 
 unsigned char rx_readc(void)