diff --git a/src/modules/px4iofirmware/px4io.c b/src/modules/px4iofirmware/px4io.c
index b20a6e1f06..b93f7a7553 100644
--- a/src/modules/px4iofirmware/px4io.c
+++ b/src/modules/px4iofirmware/px4io.c
@@ -85,7 +85,7 @@ static volatile uint8_t msg_next_out, msg_next_in;
  * output.
  */
 #define NUM_MSG 1
-static char msg[NUM_MSG][40];
+static char msg[NUM_MSG][CONFIG_USART1_TXBUFSIZE];
 
 static void heartbeat_blink(void);
 static void ring_blink(void);