diff --git a/avr/common/ringbuffer_y.asm b/avr/common/ringbuffer_y.asm
index 76c618d..4022c59 100644
--- a/avr/common/ringbuffer_y.asm
+++ b/avr/common/ringbuffer_y.asm
@@ -13,6 +13,7 @@
 .equ RINGBUFFERY_OFFS_READPOS  = 2
 .equ RINGBUFFERY_OFFS_WRITEPOS = 3
 .equ RINGBUFFERY_OFFS_DATA     = 4
+.equ RINGBUFFERY_SIZE          = 4