diff --git a/avr/twimaster.asm b/avr/twimaster.asm
index 31a224d..38eb050 100644
--- a/avr/twimaster.asm
+++ b/avr/twimaster.asm
@@ -325,7 +325,7 @@ twiReceiveByte:
   clr r17
   ldi r18, 8
 twiReceiveByte_loop:
-    rcall twiReadBit
+    rcall twiReadBit           ; (R16, R22)
     brcc twiReceiveByte_error
     lsr r16
     rol r17