diff --git a/avr/ringbuffer.asm b/avr/ringbuffer.asm
index 2f2bd84..a5bb5c9 100644
--- a/avr/ringbuffer.asm
+++ b/avr/ringbuffer.asm
@@ -63,6 +63,17 @@ RingBuffer_Alloc:
 RingBuffer_Alloc_l1:
   std y+RINGBUFFER_OFFS_WRITEPOS, r19
   mov r16, r20
+  
+  ; preset first byte (this is the length byte in COM module) with 0
+  push yl
+    push yh
+      clr r17
+      add yl, r16
+      adc yh, r17
+      st y+RINGBUFFER_OFFS_DATA, r17
+    pop yh
+  pop yl
+  
   out SREG, r21                          ; restore global interrupt enable bit in SREG
   sec
   ret