diff --git a/c/src/lib/libchip/serial/mc68681.h b/c/src/lib/libchip/serial/mc68681.h
index af0feef7cc..5642be77f7 100644
--- a/c/src/lib/libchip/serial/mc68681.h
+++ b/c/src/lib/libchip/serial/mc68681.h
@@ -25,7 +25,7 @@ extern "C" {
  */
 
 #define MC68681_STATUS          1
-#define MC68681_RX_BUFFER       2
+#define MC68681_RX_BUFFER       3
 
 #define MC68681_MODE            0
 #define MC68681_CLOCK_SELECT    1
diff --git a/c/src/libchip/serial/mc68681.h b/c/src/libchip/serial/mc68681.h
index af0feef7cc..5642be77f7 100644
--- a/c/src/libchip/serial/mc68681.h
+++ b/c/src/libchip/serial/mc68681.h
@@ -25,7 +25,7 @@ extern "C" {
  */
 
 #define MC68681_STATUS          1
-#define MC68681_RX_BUFFER       2
+#define MC68681_RX_BUFFER       3
 
 #define MC68681_MODE            0
 #define MC68681_CLOCK_SELECT    1