diff --git a/optiboot/bootloaders/optiboot/pin_defs.h b/optiboot/bootloaders/optiboot/pin_defs.h
index f3414c1..41bfc57 100644
--- a/optiboot/bootloaders/optiboot/pin_defs.h
+++ b/optiboot/bootloaders/optiboot/pin_defs.h
@@ -106,6 +106,7 @@
   #define UDR0          UDR
   #define UDRE0         UDRE
   #define RXC0          RXC
+  #define TXC0          TXC
   #define FE0           FE
   #define TIFR1         TIFR
   #define WDTCSR        WDTCR