diff --git a/Documentation/mbox_protocol.md b/Documentation/mbox_protocol.md
index 0e2c687..3907742 100644
--- a/Documentation/mbox_protocol.md
+++ b/Documentation/mbox_protocol.md
@@ -137,6 +137,13 @@
 Byte 15: BMC controlled status reg
 ```
 
+Note: when the BMC is writing a response to the mbox registers (as described
+above), the "Response Code" (Register 13) must be the last register written to.
+Writing register 13 will trigger an interrupt to the host indicating a complete
+response has been written. Triggering the interrupt by writing register 13
+prior to completing the response may lead to a data race, and must therefore
+be avoided.
+
 ## Low Level Protocol Flow
 
 What we essentially have is a set of registers which either the host or BMC can